Book of 99: Slot Overview
In this Book of 99 slot review, we focus on how the maths and features actually play out once we start spinning, rather than just admiring the artwork. We will break down how wins build across the 5x3 grid, how the dual-role book symbol can feel stubborn in the base game but central once the bonus lands, and what that unusually generous RTP means for long sessions.
Graphics & Sound: High-RTP Greek Legends
Book of 99 slot sets us on a storm-tinged Greek shoreline, the reels sunk into a marble temple front with curling columns and a stone relief to the left that doubles as the 99-step wild counter. Symbols are clean and readable: a confident hero, a veiled priestess, a snarling cyclops and a horned temptress sit above chiselled royals, while the gilt book gleams with embossed “99” and snaps attention whenever it lands. Characters hold strong eye contact between spins and feel weighty when they line up, which helps the grid pop despite the muted dusk palette. The interface keeps out of the way — bet and balance sit along the bottom bar, spin is centred, payline schemes and rules live in the menu, and that vertical meter tracks progress with a satisfying click each time a wild drops.
The audio stays measured: a calm, misty-forest motif in the base game, short voice-like stings on wins, and a distinct chime for books; in free spins the score tightens and grows a shade more dramatic without smothering the action, letting the mythic tone carry the session rather than shout over it.
Volatility & RTP
Book of 99 runs at a fixed 99% RTP and high volatility. The game’s maximum win is capped at x12,075 of your stake.
How to Play Book of 99
In the Book of 99 demo, we play with virtual funds. You start with 5,000 Fun and can reset back to that amount any time by refreshing the page. Set your stake using the “−” / “+” controls to the left of the central Spin button; the slot menu sits in the bottom-left corner. Your balance and last win are shown at the bottom-right. Autoplay and spin-speed controls aren’t available in the UK version due to regulations; in some other jurisdictions, these options appear in the menu and can be configured there.
Game Symbols and Payouts
Book of 99 pays on 10 fixed paylines from left to right. Line wins are shown below as multiples of your total bet.
| Symbol | 2 | 3 | 4 | 5 |
|---|---|---|---|---|
| Hero | x1 | x10 | x100 | x500 |
| Priestess | x0.5 | x4 | x40 | x200 |
| Cyclops / Temptress | x0.5 | x3 | x10 | x75 |
| A / K | – | x0.5 | x4 | x15 |
| Q / J / 10 | – | x0.5 | x2.5 | x10 |
Book of 99: Slot Features
Book of 99 keeps its feature set tight, letting every special symbol feed into the same expanding-symbol bonus. Most of the flavour comes from how the book behaves and how often wilds contribute to the long march toward the 99-step collection trigger.
- Book (Wild/Scatter) — substitutes for all regular symbols and can trigger free spins when 3 or more land in a single spin; it does not carry its own payouts.
- Special Expanding Symbol — chosen at the start of free spins; when enough of these land together, they expand to fill their reels.
Bonus Choice
From playtesting, the bonus seems to surface roughly every 150–250 spins, which fits the slot’s high-volatility rhythm: long stretches of steady spins broken by the occasional surge once the book finally cooperates or the collection meter fills.
- Free spins trigger when 3 or more Book symbols land anywhere in a single spin, awarding 10 free spins.
- They also trigger when the collection meter reaches 99 wilds, awarding 10 free rounds using the weighted-average stake gathered across all the wild-collecting spins.
- If both triggers occur in the same spin, the Book-triggered free spins play first, followed by the collection-triggered free spins.
- Before free rounds begin, one regular symbol is randomly selected as the special expanding symbol for the entire bonus.
- Any normal line wins are paid first before expansion is considered.
- If enough special symbols land, they expand to fill their reels (2 for premium symbols, 3 for low-pay symbols) and then pay on all 10 lines regardless of their horizontal positions.
- Existing wild symbols on the reels are ignored when determining expansions or payouts for the special symbol.
- Landing 3 or more Books during the bonus awards 10 additional spins, with the same special symbol retained.
- When the collection-triggered bonus finishes, any excess wilds above 99 are carried over into a fresh meter (e.g., 101 collected becomes 2).
Summary
Book of 99 free play shows how Relax Gaming veered away from the usual “book-slot sequel formula” and built something more deliberate, slower-burning and mathematically bold. Instead of piling on new characters or gimmicks, the studio anchored the entire game around its unusually generous 99% RTP, a high-volatility engine and the long-form wild collection that guarantees a bonus after 99 hits.
The setup feels more strategic than earlier book-style releases, with the expanding-symbol round retaining all the familiar thrills but supported by a steadier, more predictable route into it.
Players who enjoy patient, numbers-driven slots will appreciate how the meter softens the randomness without diluting the tension. At the same time, fans of the traditional expanding-symbol bonuses still get the clean, uncluttered gameplay they expect. If you want a high-ceiling book slot that rewards longer sessions and values substance over spectacle, this one stands out for the right reasons.
