Book of 99

Anyone who is looking for an exciting book that involves  extra features and a maximum win potential of more than 10,000x your bet - this is a game to consider. Book of 99 belongs to the "Book of" land of online slots but it is unlike most other games. The first thing that got my attention about this game was the intro. The number 99 is shown in a superb 3D golden model that turns slowly in a Matrix-styled manner before it slams into place.

Release date: 4 May 2021

Book of 99

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Discover the Book of 99% RTP

There is a reason why this number has been deserving to feature so prominently in the intro.
The number 99 defines the game in more than one way.

First of all, this Relax Gaming product is a rarity because its theoretical Return to Player is 99.00%. Second, you can trigger the main feature by collecting 99 scatter symbols.

Find out about the gameplay and its features from our full Book of 99 slot review. You can also claim a new casino bonus right from this page and discover slots by Relax Gaming.

Play Book of 99 Online

This slots adventure takes you to a mythological land inhabited by strange creatures and demigods. These comprise the high-paying symbols in a game of 10 paylines, three rows and five reels.

As per the usual, Book of 99 slot is a multi-payline game that can create winning outcomes on more than on line, from the same bet. This can certainly be advantageous to the player who bides his time for the bonus feature.

I am going to save this detail for later, but I'll just say that the full 10 paylines can potentially come into play to accept stacks of matching symbols.

The game has a wild symbol which can act as scatter. This is typical for "Book of" slots but in Book of 99, the wild can substitute, trigger free spins and fill the meter on the left. This triple role is definitely one of the few details that I find attractive.

About Book of 99 Slot

If you've decided to enter a mythological realm and this is a game whose features look appealing, you can begin playing by simply pressing the big, round Spin button on the right.

The default bet is usually one pound but if you want to change it, press  the coin stack  button above Spin and choose a value between 10p and £100.00 per spin.

I definitely appreciate the fact that Relax Gaming enabled players to wager as little as 10p per spin to either try the game or in the hope that the free spins bonus may shake out a stunning victory.

One  way to play Book of 99 slot is by selecting a number from the automatic spins presets. To do this you need to press the Autoplay button which is below that for Spin.

If you are set to play, claim a casino bonus or read on to find out more about my experience with this game.

Graphics, Design and Symbols

I am not going to mince my words here. I think that the graphic design is on the fence between horrendous and tolerable. The cards' symbols aren't too bad but I think Relax Gaming's artists could have done a lot better with the high-paying symbols.

The game is based on mythology so the expectation of getting a thematic kick  from the graphics comes with betting every single penny. On the other hand and for this game only, I can see past the design because of the gameplay features, the max win potential and the 99% RTP.

Sure, Book of 99 has few decent graphic features. Winning outcomes are followed by a fireball that shoots through the payline and the picture symbols spring to life, although briefly.

The detail that had me forget about the less than innovative graphic design was also the sound design. I think that most players will enjoy the audio track and the sound effects.

Book of 99 Slot Symbols, Volatility and RTP

The most important symbol in any online slot game that belongs to the "Book of" realm is the scatter/wild. In this case, that symbol is a book. No surprises there. I'll highlight the value of the top-paying symbol, represented by a centaur as probably the second symbol in terms of importance.

In terms of the symbols values, however, Book of 99 slot is astonishingly generous. You can do a little homework to find that in most online,  the cards' symbols can rarely pay 0.5x your bet for three of a kind. The unwritten rule is that these symbols usually pay less, like between 0.2x and 0.4x.

I think that the overall paytable structure is quite amazing. The Ace and King symbols can pay 15x your bet for five of a kind which is absolutely amazing. Another huge plus is that the high paying symbols can also pay for two of the same kind.

Let's look at the full paytable structure of this game:

  • 10 card: 0.5x, 2.5x, 10x
  • Jack: 0.5x, 2.5x, 10x
  • Queen: 0.5x, 2.5x, 10x
  • King: 0.5x, 4x, 15x
  • Ace: 0.5x, 4x, 15x
  • Catwoman: 0.5x, 3x, 10x, 75x
  • Cyclop: 0.5x, 3x, 10x, 75x
  • Princess: 0.5x, 4x, 40x, 200x
  • Centaur: 1x, 10x, 100x, 500x

Like I said earlier, this is a fact that doesn't need withholding until now, the RTP is a full 99% which is very, very rare. The volatility is high.

Book of 99 Slot Features


This is the main symbol of the game. The wild substitutes for all symbols, it can act as a scatter to trigger the free spins bonus and it goes into the 99 meter on the left.

Free Spins

Trigger 10 free spins by landing three Book wilds that are not part of a winning combination. Before the free rounds begin, the game chooses a special expanding symbol that expands across the full reel every time it comes into view. The special symbols can pay on all 10 lines and it doesn't need to fall on adjacent reels in order to pay for three or four fully expanded symbols.

Book Collection

Every wild/scatter that lands on the reels is automatically added to the meter on the left. Collecting 99 symbols triggers the free spins bonus. The size of the bet is also taken into account. Book of 99 pulls the average bet amount from all the bets that were wagered on the way to filling the meter.

Play Book of 99 Slot on Mobile

Most certainly, you can play this game on an iOS or Android telephone or tablet. This is possible from an online casino that is mobile ready and that is all of the casinos on our website that we have played on, reviewed and which we trust.

Other Popular Relax Gaming Slots

Mega Mine Nudging Ways Slot

Relax Gaming has come up with the Nudging Ways in order to deliver an astounding feature called Nudging Mystery Stacks. This can help you land winning outcomes as big as 50,000x your bet in an amazing gameplay with 30,000plus win-ways. The RTP of Mega Mine is 96.15% and the volatility is high. Players can win a free spins bonus that comes with the possibility to land wild stacks.

Our Final Verdict

You already know what I think about the graphic design but the gameplay itself and the potential payouts mean bees knees. Play the game for as little as 10p or one pound and try to get to the expanding special symbols’-defined bonus feature.

You can play Book of 99 slot at trusted and licensed online casinos today. Claim a casino welcome bonus from this page and begin your gaming experience.

Main Features
Provider: Relax Gaming
Reels: 5x3
Paylines: 10
Min Bets: 0.10
Max Bets: 100.00
Max Payout: 10,000x
Bonus rounds: Expanding Symbols; Free Spins
RTP: 99.00%
Variance: High

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