Book of 99 is Relax Gaming’s Greek-mythology take on the Book-of slot, with five reels, 10 lines, a 99% return and single-spin wins up to 5,000x the bet. Besides the usual three-book trigger, collecting 99 book symbols in the base game also unlocks 10 free spins, where a randomly chosen hero expands to fill whole reels. It suits players who like a simple, classic bonus and value a high long-run return over a giant top prize.
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Putting the 99% return in pounds
Relax Gaming built the game around its return, and its own page calls Book of 99 a 99RTP slot. Over time, that leaves the game about £1 of every £100 staked. A slot paying 96% keeps £4 of the same £100, so the long-run cost here is about a quarter of that.
That is an average over a very long run, not a promise for one evening. Reviews place the volatility anywhere from medium to very high, and Relax’s own scale is reported at its top grade, 5 out of 5. Bets run from €0.10 to €100 a spin on Relax’s listing.
The two top-win figures in circulation measure different things. Relax’s 5,000x is the most a single spin can pay, while the 12,075x some reviews list is the largest total a whole free-spins round has reached in simulation, retriggers included.
Collecting books towards the 99
The book does double duty, standing in for other symbols and acting as the scatter. Three or more in one spin start 10 free spins, as in any Book-of game.
What Relax added is a second road in. Books collected during the base game count towards a total, and reaching 99 also triggers the 10 free spins. Books that land without starting the round still move the counter towards 99. Relax’s listing does not say whether the count carries over a change of stake or a break in play, so the game’s help screen is the place to look.
Choosing a hero for the free spins
Before the round begins, one of the Greek warriors is picked at random. For the rest of the bonus, that hero is the expanding symbol: whenever it lands, it grows to fill its whole reel, and a few of them together can cover most of the screen.
Three or more books landing during the round add another 10 free spins. Relax ties the game’s 5,000x potential to this round and its expanding hero.
Comparing the Book-of favourites
The expanding-symbol idea is shared by several well-known games, and Book of 99 stands out mainly on return.
| Slot | RTP | Top win | Cost per £100 |
|---|---|---|---|
| Book of 99 (Relax Gaming) | 99.00% | 5,000x | £1.00 |
| John Hunter and the Book of Tut (Pragmatic Play) | 96.50% | 5,500x | £3.50 |
| Book of Dead (Play’n GO) | 96.21% | 5,000x | £3.79 |
The other two games can run at lower settings chosen by the casino, which makes the gap wider still.
Turning to more gods and books
Book of Dead is Play’n GO’s Egyptian adventure with Rich Wilde, and John Hunter and the Book of Tut is Pragmatic Play’s version with a 5,500x cap. For the Greek gods without the book, Rise of Olympus lets three of them shape a cluster-pays grid. From Relax Gaming itself, Money Train swaps the expanding hero for a respin bonus with a far higher ceiling. Our Greek mythology slots list and the Relax Gaming catalogue hold the rest.
FAQ
99%, as Relax Gaming publishes it. That is about £1 kept by the game for every £100 staked over the long run.
5,000x the bet on a single spin, as Relax gives it. Reviews report 12,075x as the largest total a whole free-spins round has reached in simulation, retriggers included.
Books collected in the base game add to a total, and reaching 99 starts 10 free spins, alongside the normal trigger of three books on one spin.
Yes. Three or more books during the round add another 10 free spins.
Stretching the budget sensibly
A high return makes a budget last longer on average, but it does not stop a session from ending early. Choose the amount and the time before you start, and leave when either runs out.
Book of 99 is only for players aged 18 or over. For free, confidential support about gambling, call the National Gambling Helpline on 0808 8020 133, run by GamCare and answered day and night.
