Book of 99 is a groundbreaking video slot from Relax Gaming that combines classic Book-style gameplay with an unprecedented 99% RTP. Set in Ancient Greece, this high volatility slot features a unique collection mechanic, free spins with expanding symbols, and a maximum win potential of 5000x your stake.
Book of 99 by Relax Gaming represents a significant milestone in online slot development, introducing the highest RTP percentage ever seen in the popular Book-style slot category. Released as a direct response to ongoing player discussions about return-to-player percentages, this Greek mythology-themed game challenges conventional thinking about how RTP impacts individual gaming sessions, particularly when combined with high volatility mechanics.
The game transports players to Ancient Greece, where mythical warriors, sorceresses, cyclopes, and harpies populate the reels against a backdrop of classical architecture. While the theme itself follows familiar territory in the crowded mythology slot segment, the 99% RTP figure sets this title apart from virtually every competitor in the market. The question remains whether this unprecedented return percentage, combined with traditional Book game mechanics, creates a genuinely superior player experience or simply serves as a marketing differentiator in an oversaturated genre.
The visual design of Book of 99 adheres closely to established conventions within the Ancient Greece slot category. The 5x3 grid sits prominently in the center of the screen, framed by stone columns that evoke classical Greek architecture. The backdrop depicts a temple or palace setting with warm, golden lighting that creates an appropriately mythological atmosphere without overwhelming the gameplay area.
Symbol design follows a two-tier approach common to Book-style slots. Lower-paying symbols utilize standard playing card values from 10 through Ace, rendered in a style that attempts to blend with the Greek theme through decorative flourishes and metallic textures. The higher-paying symbols feature four distinct Greek characters: a red-clad hero warrior, a female sorceress, a menacing cyclops, and a harpy. Each character symbol displays adequate detail and animation quality, though the artistic execution remains functional rather than groundbreaking.
The special Book symbol serves as the visual centerpiece, acting as both the Wild and Scatter symbol. Its design features golden pages with mystical inscriptions, and it animates with a subtle glow when forming part of a winning combination. The symbol's dual functionality is clearly communicated through the game's interface, reducing potential player confusion about its multiple roles.
Book of 99 operates on a straightforward mechanical foundation that will feel immediately familiar to anyone who has played Book of Ra or its numerous derivatives. The game uses 10 fixed paylines across the 5x3 grid, with winning combinations forming from left to right. Players can adjust their stake from a minimum of 0.10 to a maximum of 100 per spin, providing flexibility for both conservative and aggressive betting strategies.
The paytable structure divides symbols into clear value tiers. Low-paying card symbols require at least three matching symbols on a payline to award a win. High-paying character symbols are more generous, paying out for just two matching symbols on a payline. The premium symbol, the red-clad hero warrior, delivers the highest base game payout at 500x the bet for landing five of a kind. The cyclops, sorceress, and harpy offer progressively lower payouts, ranging from 75x to 250x for five-symbol combinations.
The Book symbol's Wild functionality allows it to substitute for all other symbols to complete winning combinations, a standard feature that increases hit frequency during base game play. This substitution mechanic operates automatically, with the game engine calculating the highest possible win for any given spin result.
The most distinctive base game mechanic in Book of 99 is the collection meter displayed on the left side of the screen. This feature adds a progressive element to the standard Book game formula, addressing one of the most common criticisms of the genre: the lack of engagement during base game play.
Every time a Book symbol lands anywhere on the reels during the base game, it contributes to the collection meter. The meter tracks progress toward the 99-book threshold, with a visual indicator showing how many books have been collected. This mechanic creates a secondary objective beyond simply landing winning combinations, giving players an additional reason to continue spinning even during dry spells.
When the meter reaches 99 collected books, the game automatically triggers 10 free spins, providing an alternative route to the bonus round beyond the traditional three-scatter trigger. This dual-trigger system increases the overall frequency of bonus round access, though the high number of required collections means players should expect this trigger method to occur relatively infrequently compared to the standard scatter trigger.
The Free Spins feature represents the primary bonus mechanic and the main source of significant win potential in Book of 99. Players can trigger this round through two distinct methods: landing three or more Book scatter symbols anywhere on the reels during a single spin, or collecting 99 books through the base game collection meter.
Regardless of the trigger method, players receive an initial allocation of 10 free spins. Before the free spins begin, the game randomly selects one of the four high-paying character symbols to serve as the special expanding symbol for the duration of the bonus round. This selection process occurs through an animated sequence that cycles through the available symbols before landing on the chosen character.
The selected special symbol gains expanding properties during free spins, fundamentally altering how wins are calculated. When the special symbol lands on the reels during a free spin, it expands to fill all three positions on its reel before wins are evaluated. Importantly, the special symbol does not need to appear on adjacent reels or follow standard payline rules when expanded. Instead, it pays in a scatter-style fashion, awarding wins based on the total number of symbols visible anywhere on the screen after expansion.
This mechanic creates the potential for substantial wins, particularly when the special symbol appears on multiple reels simultaneously. If the special symbol lands on three or more reels and expands, it can fill significant portions of the game grid, resulting in multiple simultaneous winning combinations. The expanding symbol also pays for non-adjacent appearances, meaning symbols on reels 1, 3, and 5 will still award a win even without symbols on reels 2 and 4.
Book of 99 operates on a classic 5x3 grid with 10 fixed paylines, offering wins that pay from left to right. The game features a balanced paytable with 10 symbols total: 5 low-paying card symbols and 4 high-paying Greek character symbols, plus the special Book symbol that serves dual functions as both Wild and Scatter.
The slot is built on high volatility mathematics, meaning wins may be less frequent but potentially more substantial. The 99% RTP represents the highest return-to-player percentage in the Book-style slot category, calculated over millions of spins to provide long-term theoretical returns to players.
The Free Spins round includes a retrigger mechanism that can extend the bonus session indefinitely in theory. Landing three or more Book scatter symbols during any free spin awards an additional 10 free spins, which are added to any remaining spins from the current bonus round. There is no stated limit to the number of times free spins can be retriggered, allowing for the possibility of extended bonus sessions that accumulate substantial wins over dozens of spins.
The retrigger mechanic does not change the selected expanding symbol. Once a character is chosen at the start of the bonus round, it remains the special symbol for all spins in that bonus session, including any retriggered spins. This consistency allows players to develop a sense of which symbols might deliver the best results based on their frequency of appearance and payout values.
The 99% RTP figure represents the most heavily marketed aspect of Book of 99, and it warrants careful examination to understand what this percentage actually means for player experience. Return-to-player percentage is a theoretical statistical measure calculated over millions of simulated spins. It indicates that, over an extremely long period, the game will return 99% of all wagered money to players in the form of wins, with the remaining 1% representing the house edge.
For individual players in typical gaming sessions, RTP functions more as a comparative metric than a predictive tool. A 99% RTP is objectively superior to the industry standard of 96% or the lower RTPs of 94% or 92% found in many competing slots. Over thousands of spins, a player on Book of 99 should theoretically experience better overall returns than on a comparable game with a 96% RTP. However, the high volatility rating significantly impacts how these returns are distributed.
High volatility means wins occur less frequently but tend to be larger when they do hit. In practical terms, players should expect longer periods without significant wins, punctuated by occasional larger payouts. The combination of 99% RTP with high volatility creates an interesting mathematical profile: the game returns more money overall, but that money comes in less predictable, more concentrated bursts. This profile suits players with sufficient bankroll to weather dry spells while waiting for bonus rounds or significant base game hits.
Book of 99 advertises a maximum win potential of 5000x the bet amount, which translates to a maximum possible payout of 500,000 in currency units when playing at the maximum stake of 100. This maximum win figure is respectable but not exceptional when compared to modern high volatility slots, some of which offer maximum wins exceeding 10,000x or even 50,000x.
The 5000x maximum win is most likely to occur during an extended Free Spins session with multiple retriggers, where the expanding symbol mechanic creates numerous high-value combinations across many spins. Achieving wins approaching this maximum would require exceptional luck in terms of both the frequency of special symbol appearances and the number of retriggers obtained.
The base game maximum win is considerably more modest, capped at 500x for landing five of the top-paying hero symbols on a single payline. Even with multiple simultaneous payline wins and Wild substitutions, base game wins rarely exceed 100x to 200x the bet amount in typical play. This distribution reinforces that the Free Spins round represents the primary win potential, with base game play serving mainly to build the collection meter and provide occasional smaller wins to extend playing time.
The Book-style slot category is among the most crowded in the online casino market, with dozens of titles competing for player attention. Book of 99 enters this competitive landscape with its RTP as the primary differentiator, but how does it compare in other aspects?
Compared to the genre-defining Book of Ra, Book of 99 offers a significantly higher RTP (99% versus 95-96% for various Book of Ra versions) and a more engaging base game through the collection mechanic. However, Book of Ra benefits from stronger brand recognition and a more established player base. The core bonus mechanics are nearly identical, with both games using the expanding symbol concept during free spins.
Against more recent Book-style competitors, Book of 99 holds its own primarily through the RTP advantage. Many modern Book slots offer additional features such as gamble options, multiple expanding symbols, or progressive jackpots. Book of 99 takes a more conservative approach, focusing on refined execution of core mechanics rather than feature proliferation. This approach may appeal to players who prefer straightforward gameplay without excessive complexity.
Book of 99 is built using HTML5 technology, ensuring full compatibility across desktop, tablet, and mobile devices without requiring separate app downloads. The game adapts its interface to different screen sizes, maintaining functionality and visual clarity on devices ranging from large desktop monitors to smartphone screens.
On mobile devices, the game interface reorganizes to accommodate touch controls and smaller displays. The betting controls and game information panels become accessible through expandable menus, keeping the reels as the primary focus of the screen. The collection meter remains visible on mobile, though it may be repositioned or resized depending on the device orientation and screen dimensions.
Technical performance across devices is generally smooth, with the game loading quickly and maintaining consistent frame rates during spins and animations. The relatively simple graphics and animation style contribute to stable performance even on older mobile devices or slower internet connections.
Book of 99 succeeds in its primary objective: delivering the highest RTP percentage in the Book-style slot category while maintaining the core gameplay elements that define the genre. The 99% return-to-player figure is not merely a marketing gimmick but a genuine mathematical advantage that should result in better long-term returns for players compared to competing titles with standard 96% RTPs.
However, the game's high volatility means this RTP advantage manifests over extended play sessions rather than in any single gaming session. Players must approach Book of 99 with appropriate bankroll management and realistic expectations about win frequency. The 5000x maximum win potential, while substantial, is not exceptional by modern standards, and players seeking the highest possible maximum wins may find more appealing options elsewhere.
The collection mechanic adds meaningful engagement to base game play, addressing one of the most common weaknesses of Book-style slots. The dual trigger system for free spins provides psychological variety, even if the collection trigger occurs relatively infrequently in practice. The Free Spins round itself executes the expanding symbol mechanic competently, with the retrigger potential offering the possibility of extended bonus sessions.
Book of 99 is best suited for players who prioritize RTP above all other factors, who enjoy traditional Book-style gameplay, and who have the bankroll to accommodate high volatility swings. It represents a solid, well-executed entry in a crowded genre, distinguished primarily by its mathematical generosity rather than innovative features or exceptional production values.
The 99% RTP is the highest return-to-player percentage available in Book-style slots and among the highest in the entire online slot industry. This means the game theoretically returns 99% of all wagered money to players over millions of spins, compared to the industry standard of 96%, resulting in better long-term value for players.
Every Book symbol that lands on the reels during base game play is added to a collection meter displayed on the side of the screen. When you collect 99 Book symbols, the game automatically triggers 10 free spins, providing an alternative way to access the bonus round beyond the traditional three-scatter trigger.
Yes, landing three or more Book scatter symbols during any free spin awards an additional 10 free spins. There is no limit to the number of retriggers possible, allowing for extended bonus sessions that can accumulate substantial wins over multiple rounds.
The maximum win in Book of 99 is 5000x your bet amount. At the maximum stake of 100, this translates to a potential payout of 500,000 in currency units. This maximum win is most likely achieved during extended free spins sessions with multiple retriggers and favorable expanding symbol appearances.
Before free spins begin, one of the four high-paying character symbols is randomly selected as the special expanding symbol. When this symbol appears during free spins, it expands to fill all three positions on its reel. The expanded symbol pays in a scatter-style fashion based on total symbols visible, not requiring adjacent positions or standard payline rules.
Book of 99 features high volatility, meaning wins occur less frequently but tend to be larger when they hit. This volatility profile typically requires a larger bankroll to sustain play through dry spells. While the minimum bet of 0.10 is accessible, the high volatility makes this game more suitable for players with adequate bankroll reserves and patience for variance.
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