Book of 99
Book of 99 is Relax Gaming’s take on the classic “Book of” slot format, with one headline difference: a theoretical return of 99%, far above the 94% to 96% typical for the genre. The setting is ancient Greece, the rules follow the familiar formula of a Book symbol acting as wild and scatter and a random expanding symbol in free spins, and there is an added twist in the base game, a meter that triggers the bonus once you have collected 99 Books.
This review explains how the game plays, how the collection meter works, what the expanding symbol does in free spins and what a 99% RTP really means for your bankroll. Figures come from Relax Gaming’s official game page and independent game databases; as with any slot, confirm the RTP in the game rules at your casino.
Where to Play Book of 99
Book of 99 is available at casinos that offer Relax Gaming games. The casinos below are reviewed on BetsAuthority, accept Australian players and list Relax Gaming among their providers. Open the in-game info to confirm the RTP setting before you play.
Quick Facts About Book of 99
| Parameter | Details |
|---|---|
| Slot | Book of 99 |
| Provider | Relax Gaming |
| Release | May 2021 |
| Layout | 5 reels / 3 rows |
| Paylines | 10 |
| RTP | 99% |
| Volatility | High |
| Bet range | 0.10 to 100 per spin (casino limits may differ) |
| Maximum win | 12,075x the stake (per game databases) |
| Free spins | 10 spins for 3+ Books or 99 collected Books |
| Special symbol | Book (wild and scatter) |
How Book of 99 Works
The game uses a 5×3 grid with 10 paylines that pay from left to right. Low-value symbols are the familiar card royals, 10 through A. The premium set is made up of figures from Greek myth: Polyphemus and Lamia, Pythia, and Apollo at the top. Premium symbols pay from just two on a line, while the royals need three. Independent paytables list five Apollo symbols on a line at 500x the total stake, so a full-screen top symbol win across all 10 lines comes to 5,000x the total stake.
The Book symbol does double duty. As a wild, it substitutes for every regular symbol to complete lines. As a scatter, three or more anywhere trigger free spins.
The 99 Books Collection Meter
Book of 99 adds a collection feature that most “Book of” games do not have. Every Book symbol that lands in the base game is counted on a meter, represented by a ship sailing towards home. When the count reaches 99 Books, the free spins feature is triggered automatically, exactly as if three scatters had landed.
The meter gives a second, guaranteed route into the bonus. It does not change the RTP, which already takes it into account, but it does change how the game feels: dry spells are capped, because every Book you land brings you closer to a trigger. The meter is a useful thing to watch when deciding whether to keep playing or stop at your limit, since stopping near 99 means losing that progress.
Free Spins and the Expanding Symbol
Three or more Books, or a full meter, award 10 free spins. Before the round starts, one regular symbol is chosen at random to be the expanding symbol for the whole feature.
- If the chosen symbol is one of the character premiums, it needs at least 2 on the reels to expand.
- If it is a royal, it needs at least 3.
- When enough land, the symbol expands to cover each reel it appears on and pays across all 10 lines, even on non-adjacent reels.
Expansion happens after the regular wins are paid, so you receive both. Landing 3 or more Books during the feature awards another 10 free spins, and the expanding symbol stays the same. The biggest wins come from a premium character expanding on all five reels, ideally several times in a retriggered round.
RTP: What 99% Means
At 99%, Book of 99 has a theoretical house edge of 1%, compared with about 4% for a typical 96% slot. Over a very large number of spins, that means more of the money staked comes back to players as a group. It does not mean individual sessions are safe. The game is rated high volatility, so most of the return is concentrated in free spins with a strong expanding symbol, and many sessions will lose in the short term.
Operators can choose different configurations of a game, so always check the RTP line in the game rules at your casino before you play for money.
Worked Example: An Expanding Symbol Win
Say you bet A$1 (10 cents per line) and trigger free spins, and Pythia is chosen as the expanding symbol. On one spin, Pythia lands on reels 1, 3 and 5. First the normal line wins are paid. Then the three Pythia symbols expand to fill reels 1, 3 and 5, and the game pays three-of-a-kind Pythia on all 10 lines, even though the reels are not next to each other.
If a royal had been chosen instead, the same expansion would need at least three symbols and would pay much less. This is why the choice of expanding symbol has such a big effect on the result of each round.
The best case is Apollo. If five Apollo symbols cover all reels after expanding, every one of the 10 lines pays the top five-of-a-kind prize, which adds up to 5,000x the stake on a single spin. Retriggers keep the same expanding symbol, so a round with Apollo chosen and an extra 10 spins is where the published maximum of 12,075x becomes possible. Such rounds are very rare, and most bonus rounds pay a small fraction of that.
Bankroll Tips for Book of 99
- A high RTP does not reduce volatility; budget for at least 200 to 300 spins.
- Keep track of the Book meter, but do not exceed your limit just to reach 99.
- Avoid raising your stake after a losing run; outcomes are independent.
- Set loss and time limits before starting and use your casino’s deposit limit tools.
- Every spin is decided by a certified random number generator, regardless of meter progress.
Pros and Cons of Book of 99
| Pros | Cons |
|---|---|
| 99% RTP, well above most slots | High volatility despite the high RTP |
| 99 Books meter gives a second route to free spins | Royal expanding symbols pay little |
| Expanding symbol pays on non-adjacent reels | Familiar Book-style base game |
| Retriggerable free spins | No bonus buy listed by the provider |
| Wide bet range from 0.10 to 100 | Big wins rely on a premium expanding symbol |
How It Compares With Other Book Slots
Most games in the genre follow the same template: a 5×3 grid, 10 lines, a Book that is both wild and scatter and a random expanding symbol. Book of 99 keeps that template, so it will feel familiar straight away. The two differences that matter are the much higher RTP and the collection meter, which together make it one of the more player-friendly Book games on paper, while keeping the same high-volatility character.
Demo Play vs Real Money
Relax Gaming provides a free-play version of Book of 99 through its demo launcher and partner casinos, although availability depends on your location. The demo uses the same maths as the real game, so it is a good way to see how quickly the Book meter fills and how different expanding symbols perform.
For real money play, choose a licensed casino with clear RTP disclosure, verified withdrawals and responsible gambling tools. Compare options in our casino reviews.
Frequently Asked Questions
Book of 99 is built around a 99% RTP, which is the point of its name. Still, open the game rules at your casino to confirm the figure, as operators can run different configurations of a game.
Game databases list the maximum win at 12,075x the stake. A screen full of the top symbol in free spins pays 5,000x, which is the figure Relax Gaming highlights in its description.
Land 3 or more Book symbols on one spin for 10 free spins, or collect 99 Books on the meter during the base game, which also triggers the feature.
The meter fills as Books land in the base game, so each Book you land moves you closer to a guaranteed bonus trigger at 99.
Yes. Landing 3 or more Book symbols during free spins awards another 10 free spins.
A 99% RTP means a lower theoretical house edge than most slots, but it is a long-term average. The game is high volatility, so short sessions can still lose quickly.
Responsible Gaming Note
Book of 99 is entertainment, not a way to earn money, and a high RTP does not change that. Only play if you are 18 or older, set limits before you begin and stop when you reach them. If gambling stops being fun, free and confidential support is available 24/7 from Gambling Help Online on 1800 858 858.
Final Verdict
Book of 99 takes a well-known format and gives it two genuine improvements: a 99% RTP and a collection meter that guarantees a bonus after 99 Books. The free spins work as fans of the genre expect, with an expanding symbol that can fill the screen and a published maximum of 12,075x. Volatility remains high, so it still calls for a sensible budget, but for Book slot fans it is one of the strongest options available.
