Book of 99 Slot Review
Relax Gaming have carved out a niche with their distinct approach to ancient mythology slots, and Book of 99 showcases this with a unique twist on the well-established ‘book of’ formula. Released in May 2021, the game introduces a collection meter system that differentiates it from the countless Book of Ra derivatives saturating the market. While Greek mythology remains a proven gold mine for slot developers, with competitors like Amazing Link Apollo and Helios’ Fury drawing from the same cultural well, Book of 99’s collection mechanic and exceptional 99% RTP provide tangible points of distinction. The game targets RTP-conscious players seeking value alongside high-volatility excitement, though those prioritising frequent smaller wins may find the experience challenging.
Base Game & Features
Book of 99 operates on a standard 5-reel, 3-row configuration with 10 fixed paylines. The game grid follows the traditional setup familiar to anyone who has encountered the ‘book of’ archetype, with wins formed by matching symbols across left-to-right paylines. Ancient Greek mythology provides the visual framework, featuring character symbols including Odysseus, Cyclops, and other figures from Homer’s Odyssey alongside lower-paying royal card symbols (10 through A).
The Book symbol serves dual functions as both wild and scatter, substituting for all other symbols to complete winning combinations while simultaneously acting as the scatter trigger for the bonus round. This dual-purpose mechanic is central to the game’s structure, creating both base game win potential and feature activation opportunities. Landing the Book wild contributes to the collection meter system (detailed below), adding strategic depth to its appearance beyond immediate line wins.
Bets range from £0.10 to £100 per spin, accommodating casual players through to high-stakes enthusiasts. The paytable scales proportionally with stake, with Odysseus serving as the top-value character symbol. The hit frequency of 29.83% means approximately one winning spin in every 3.35 spins, which sits below average and aligns with the game’s high volatility (5/5 rating). Base game pacing reflects this volatility profile, with prolonged periods between significant wins punctuated by occasional larger payouts when premium symbols align.
Book Collection Feature
The collection meter represents Book of 99’s primary innovation within the ‘book of’ framework. Each Book wild symbol that lands during base gameplay adds to the collection meter, visualised by Odysseus’ ship progressing upward. Accumulating 99 Book wilds fills the meter completely and triggers 10 free spins, providing an alternative activation path alongside the traditional scatter trigger.
The meter persists when changing stakes mid-session, meaning collected wilds carry forward regardless of bet adjustments. When the meter triggers the bonus round, free spins are played at the average stake used during the collection period rather than the current stake level. This mechanic introduces strategic considerations around stake management that aren’t present in standard book slots, though it can also create frustration when the meter progresses slowly during dry spells.
Book of 99 Free Spins
Free spins activate via two methods: landing 3 or more Book scatter symbols anywhere on the reels during a single spin, or filling the collection meter with 99 wilds. Both paths award 10 free spins. Before the bonus round begins, one symbol is randomly selected to act as the expanding symbol throughout the feature.
During free spins, the selected symbol expands to cover entire reels when sufficient instances appear. Character symbols require 2 or more on the screen to trigger expansion, while royal card symbols require 3 or more. When expansion conditions are met, symbols expand across their entire reel before pays are evaluated, creating the potential for full-screen coverage of premium symbols. Expanding symbols pay on any position across the reels, not requiring traditional payline alignment.
The bonus round can retrigger by landing 3 or more scatter symbols during free spins, awarding an additional 10 spins with the same expanding symbol. Maximum win potential reaches 12,075x stake, achieved when the top-value Odysseus symbol expands across all five reels during the bonus round. Single spins are capped at 5,000x, with the 12,075x representing the round maximum across multiple free spin outcomes. The probability of hitting maximum win sits at approximately 1 in 697,350, reflecting the game’s extreme volatility profile.
No bonus buy feature is available, meaning players must trigger the round organically through either scatter activation or collection meter completion.
Our Honest Verdict
Book of 99 occupies an interesting position within the crowded ‘book of’ slot landscape, primarily distinguished by its collection meter system and exceptional 99% RTP. The math model is genuinely unusual, with the RTP figure sitting 3-4 percentage points above industry standard (typically 95-96%). For RTP-conscious players, this represents substantial value over extended play sessions, though the high volatility (5/5) ensures that bankroll swings remain significant despite the generous return rate.
The collection feature provides novelty amid otherwise standard book mechanics. Watching Odysseus’ ship progress upward adds a secondary objective to base gameplay, though the 99-wild requirement means completion often requires several hundred spins. This can prove frustrating during dry spells when the meter crawls forward with minimal win activity. The expanding symbol bonus round itself follows conventional ‘book of’ structure without meaningful innovation beyond the alternative activation method.
Relax Gaming maintain their reputation for quality presentation, with solid Ancient Greek mythology visuals and clear interface design. The game doesn’t break significant new ground mechanically beyond the collection system, positioning it as a solid but conventional entry in the developer’s portfolio. Against established competitors like Book of Dead and Legacy of Dead, Book of 99 holds its own primarily through the RTP advantage and collection meter differentiation rather than revolutionary gameplay innovation.
The maximum win of 12,075x sits slightly above average for high-volatility book slots, though it won’t satisfy players chasing truly massive multipliers available in more volatile modern releases. Target audience is clearly defined: RTP-focused players with patience and adequate bankroll to weather the high volatility. Those prioritising frequent smaller wins or seeking mechanical innovation beyond the collection system should look elsewhere. For its intended audience, Book of 99 delivers on its core promise of value-conscious high-volatility gameplay within a proven archetypal framework.
Book of 99 FAQs
Book of 99 has an exceptional 99% RTP, significantly higher than the industry standard of 95-96%. This means the game theoretically returns 99% of wagered funds to players over the long term, making it one of the most generous slots available for RTP-conscious players.
The maximum win potential is 12,075x your stake, achieved when the top-value Odysseus symbol expands across all five reels during the free spins bonus round. Single spins are capped at 5,000x, with the 12,075x representing the cumulative round maximum. The probability of hitting this maximum win is approximately 1 in 697,350 spins.
Yes, Book of 99 awards 10 free spins through two activation methods: landing 3 or more Book scatter symbols anywhere on the reels, or collecting 99 Book wild symbols to fill the collection meter. During free spins, a randomly selected symbol expands to cover entire reels when sufficient instances appear, with potential to retrigger for additional spins.
Yes, Book of 99 is fully optimised for mobile play across iOS and Android devices. The game is built using HTML5 technology, ensuring seamless performance on smartphones and tablets without requiring app downloads. All features, including the collection meter and free spins bonus, function identically on mobile and desktop platforms.
No, Book of 99 does not include a bonus buy feature. Players must trigger the free spins bonus round organically, either by landing 3 or more scatter symbols during base gameplay or by collecting 99 Book wild symbols to fill the collection meter. This design choice aligns with regulations in certain markets that prohibit feature purchase options.
Book of 99 is rated as high volatility (5 out of 5 on most volatility scales), meaning wins are infrequent but can be substantial when they occur. The hit frequency of 29.83% (approximately 1 win in every 3.35 spins) confirms this rating. Players should expect extended periods without significant wins, making adequate bankroll and patience essential despite the generous 99% RTP.
The Book Collection meter tracks Book wild symbols that land during base gameplay. Each Book wild adds to the meter, visualised by Odysseus’ ship progressing upward. Collecting 99 Book wilds fills the meter completely and triggers 10 free spins. The meter persists when changing stakes mid-session, and the free spins are played at the average stake used during the collection period. This provides an alternative bonus activation path alongside the traditional scatter trigger.
