Book of 99

Book of 99 is a high-volatility online slot developed by Relax Gaming, set in a stylised ancient Greek world. This classic “book-style” slot features expanding symbols in its bonus rounds, sculpted artwork, and a mathematically generous RTP. The game runs on a conventional 5x3 reel layout with 10 fixed paylines, offering simple mechanics enhanced by powerful features and a 99% theoretical return.

Theme and graphics

Thematically, Book of 99 draws from classical Greek mythology, distinguishing itself from the Egyptian aesthetic typical of similar titles. The background depicts a coastal shrine, with columns and cascading waves in sapphire hues. Character symbols represent mythological figures such as warriors, priestesses, and sirens. The design employs hand-drawn artistry over CGI styles, imparting a refined visual finish, while ambient music with Mediterranean tonalities reinforces the thematic immersion.

Graphical transitions are subtle yet fluid, with only minimal motion during spins and animations, supporting fast-paced play. The aesthetic focus on archetypes and ancient motifs blends seamlessly with the understated audio cues, providing thematic consistency without overwhelming the interface.

Gameplay and features

Book of 99 is structured around a traditional 5-reel, 3-row configuration with 10 non-adjustable paylines. Wins are awarded from left to right, starting from the leftmost reel. All symbols pay on three or more of a kind, except for the warrior symbol, which pays from two onwards. The titular Book symbol serves dual functions as both Wild and Scatter.

In the base game, symbol values range from low-tier card ranks (10 to Ace) to high-paying character symbols. The Book symbol substitutes for all other symbols, forming part of both regular wins and contributing to bonus triggers. Players benefit from a secondary collection feature that gradually builds towards bonus entry, providing deterministic access to free spins over longer play sessions. Mobile compatibility is seamless, allowing fluid gameplay alongside South African pay-by-phone casinos, where players can transact efficiently from mobile networks.

Bonus rounds and free spins

How to trigger bonuses

The free spins feature is triggered by landing three or more Book symbols anywhere on the grid, regardless of payline alignment. Upon activation, players are awarded 10 free spins. Additionally, a collection mechanic tracks each Book landed across base game spins, and upon collecting 99 symbols, the bonus is automatically activated, independent of scatter positioning.

This dual-path activation ensures reliable access to the bonus round, either through conventional random triggers or via deterministic progression. For jurisdictions that support it, Relax Gaming may include a Bonus Buy feature allowing instant access to the free spins for a set stake multiplier, although local legislative limitations may apply.

Special mechanics of Book of 99

During the free spins feature, one standard symbol is randomly selected to become an "expanding symbol". When this symbol appears in the free spins, it expands to cover the entire reel if it contributes to a win. Critically, these expanding symbols pay even on non-adjacent positions, which significantly increases payout opportunities.

The Book symbol continues to act as a Wild during free spins, and the feature can retrigger if three more Book symbols land during free spins, granting an additional set of 10 spins. The expanding symbol remains the same for retriggered sessions, enabling compounding potential. This symmetry holds strong appeal for players seeking consistency and long-term bonuses, especially when paired with no deposit casino offers, which may allow exploration of the bonus round without financial risk.

Payout potential and volatility

Book of 99 RTP explained

Book of 99 delivers a notable RTP figure of 99%, unprecedented among high-volatility slots. This figure stands far above the industry standard of approximately 96%. RTP, or Return to Player, refers to the theoretical percentage of wagered money a slot returns to players over long-term play. A higher RTP translates to lower average house edge, making Book of 99 one of the most player-favourable slots currently available in the regulated market.

This 99% rate allows minimal value loss per spin, which, while not guaranteeing short-term wins, supports overall session sustainability. For informed players, especially those engaging in bonus wagering or strategic bankroll management, this RTP makes the slot highly efficient.

Volatility details

Despite its favourable RTP, Book of 99 is classified as a high-volatility slot. In practical terms, this means that wins occur less frequently, but their magnitude, when triggered, tends to be significantly higher. Volatility pertains to the risk-reward profile of the slot, and Book of 99 aligns with titles designed for players willing to weather dry periods in the anticipation of substantial returns.

Bonus features may hit relatively infrequently through natural gameplay, adding strategic usefulness to the collection meter. High variance suits players with sufficient bankroll and patience, particularly within real money slot sites offering strong wagering flexibility.

Book of 99 max win potential

The primary advertised maximum win in Book of 99 is set at 5,000x the player’s stake. However, Relax Gaming lists a theoretical ceiling of up to 12,075x under specific sequences, particularly when high-paying premium symbols expand during retriggered bonus chains. Achieving maximum returns realistically requires capturing multiple expanding premium symbols in back-to-back bonus rounds, often supplemented by retriggers and favourable reel alignment.

These top-end scenarios, while statistically rare, remain within definable reach due to the mechanics involved. Compared to similar “book-style” slots such as Book of Dead or Legacy of Egypt, Book of 99 presents a comparable top-end win but outperforms through its superior RTP. It balances volatility with statistical fairness more efficiently than most of its genre contemporaries.

Final verdict on Book of 99 slot

Book of 99 achieves a rare balance in the online slot landscape, combining ultra-high RTP with classic, proven mechanics in a visually appealing package. Its collection feature accommodates extended sessions and mitigates the impact of variance by guaranteeing bonus entries over time. Its high volatility and max win potential match the expectations of serious players, while its simplicity favours those new to book-style mechanics. This slot is ideally suited to mathematically inclined players prioritising long-term expected value and sustained engagement over cosmetic novelty or feature overload.