Book of 99

Review, Demo Play, Payout, Free Spins & Bonuses

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  • Two ways to trigger free spins
  • Classic book of bonus feature
  • 99% RTP is much higher than average
  • Despite variance, bigger wins are hard to come by

Book of 99 is a 10-payline online slot developed by Relax Gaming. Features included a bonus meter, symbol collection feature, expanding symbols and free spins. The RTP of this high volatility slot is 99% and its top prize is worth 12,075x.


Relax Gaming brings players a more scaled-back experience in Book of 99 – but, there’s more than meets the eye in this 10-payline slot. The game comes with an impressive 99% RTP and allows players to trigger free spins (with the classic expanding symbols feature) in two ways.

This slot will be released at online casinos on May 4th, when you’ll also be able to play the Book of 99 free play demo here at Slots Temple. In the meantime, we’d recommend playing Book of Dead for a slot with a similar bonus or Blood Suckers for a slot with a higher-than-average RTP.

Theme and Graphics

Book of 99 is a Greek mythology-themed slot from Relax Gaming. The graphics are rendered in a unique comic book style that brings the legends of Greek myth to life in a new way. Like all Relax Gaming slots, there really isn’t anything to complain about in terms of its design. Book of 99 is a fantastic-looking slot that draws players in with its aesthetics.

Book of 99

How to Play

The game controls for Book of 99 are pretty straight forward:

  1. Once the game loads, click on the three bars in the bottom right-hand corner of the screen. This will take you to view the paytable and in-depth rules.
  2. From this menu, you can also adjust audio settings.
  3. To adjust your wager, you can use this menu, or click on the coin symbol above the spin button. Wagers between .10 coins and 100 coins are available.
  4. Click on the fast-forward button at the top of the game to turn up the spin speed.
  5. Hit the spin button and enjoy!

Book of 99 RTP and Variance

Relax Gaming’s Book of 99 brings players something we really haven’t seen before – an RTP of 99%. While many slot makers are experimenting with expanding reels and all sorts of interesting mechanics, Relax is tinkering with the maths.

It’s very uncommon for an online slot to have an RTP of anything higher than 97% - and, even that is a stretch. Most games tend to fall between 96% and 96.5%, so this is very unusual. However, we’re not complaining. It’s great to see a developer go for a maths model that is much more generous than you’ll find in the average slot.

Book of 99 is also a highly volatile online slot game. It's win rate is 29.83%, which is a little bit higher than you'd find on other high variance games - but, remember, you do still have a longer wait in between wins than you'd have in a lower variance slot. 

How to Win

There are 10 paylines in Book of 99, and wins are created by landing three or more matching symbols on any of them. The lower paying symbols are your typical poker ranks with payouts ranging from .5x to 15x your stake.

The higher paying symbols are various symbols from Greek mythology. These symbols all pay out of 2-of-a-kind combinations and above, which likely contributes to the high RTP of this slot.  

Free Spins and Bonuses

When you land three book symbols on the reels, you’ll trigger the free spins round. During this bonus, one symbol is selected to be the expanding symbol.

When this symbol appears on the reels, it will always expand and pay as a scatter. This is the feature that you’ll find in most “book of” slot games, and it’s become hugely popular in the gaming market.

Book of 99 Slot Review

Book of 99 is one of Relax Gaming’s simpler slots but it has lots going for it. The game’s incredibly high RTP brings players an engaging online gaming experience that allows you to enjoy your experience without relying on lots of different, complicated features.

Another plus of the game is the collection feature. Collecting the wilds is fun and it’s not a complete slog like you normally expect from this kind of bonus.

The free spins bonus is, of course, pretty standard for a book of slot – but, we don’t mind. It’s great that you can trigger it using two different methods, adding another layer of creativity to the gameplay.

Book of 99 is sure to be a big hit in the online slots market. It’s simple yet effective, when it comes to gameplay. More modern players might want a lot more features in their slots, but they shouldn’t discount playing Book of 99, as this game really doesn’t need all of the bells and whistles to provide a great gaming experience.

Disclaimer: Book of 99 trademark / license is owned by Relax Gaming. This site is not endorsed by Relax Gaming.

* Although we try and match games with Casinos that have them, we advise that you double-check the slot content on the casino before making a deposit.

Slot Data
Slot Name: Book of 99
Software: Relax Gaming
RTP: 99%
Volatility: High volatility
Paylines: 10
Reels: 5
Min Bet (all lines covered): £0.10 (GBP)
Max Bet: £100 (GBP)
Top Win: 12075
Features: Wild Symbol , Scatter Symbol , Free Spins , High volatility , 5 Reels , Stacked Symbols
UK Available in GB? Yes. Relax Gaming have a UKGC license and are allowed to offer their games at UK licensed casinos.

Book of 99 Slot FAQs

What is the RTP of Book of 99?

Book of 99 has a payout of 99%. This is much higher than you tend to see in online slots. In fact, we can’t think of many games that exceed this; the only one that comes close is NetEnt’s Blood Suckers with an RTP of 98%.

How volatile is Book of 99?

Book of 99 is a high volatility online slot with a top prize to match – 12,075x your stake.

How does the collection feature work in Book of 99?

Whenever you land a wild symbol, it will charge the collection meter. Once you’ve collected 99 symbols, you’ll trigger the free spins bonus.

Can you retrigger the free spins round in Book of 99?

No matter how you trigger the free spins bonus, it can be retrigger by landing three more scatters. You’ll get 10 more free spins each time you retrigger the bonus.

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