Book of 99 Slot Review

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Relax Gaming
Ancient Greece
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Book of 99 is a video slot from Relax Gaming inspired by Homer’s Odyssey. The game was released in May 2021, attracting attention due to several unique mechanics and an unprecedented RTP of 99%.

During his 10-year journey, Odysseus meets various creatures and faces all sorts of challenges, which is very nicely conveyed in the slot (we’re given a small cinematic intro and all).

But is there anything else that makes Book of 99 unique apart from its theme and a high RTP? Let’s find out!

Book of 99 Gameplay

Where Can I Play Book of 99?

Book of 99 gained the attention of many online casinos, primarily due to its high return figure and because it was made by Relax Gaming, a company known for quality releases. A few dozen legal UKGC-licensed casinos feature this title, and we’re sure more will add it soon enough.

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The game uses a standard 5×3 reel and ten fixed paylines. The card marks 10 through A represent low-value symbols, while high-value symbols include the characters of the Odyssey, including Odysseus himself — the highest-paying symbol.

The book with 99 engraved on it represents the scatter and the wild. It replaces all other symbols to create a win. You need three of them to appear anywhere on the reels after a single spin to unlock the bonus game.

The betting range in Book of 99 goes from £0.1 to £100. The game has high variance, which means you might need to be patient before hitting big, but considering this slot’s high RTP, the waiting pays off.

Book of 99 Bonus Features

Book of 99 has a single bonus game that can be triggered in two ways. The quicker and simpler method is to get three or more books to land anywhere on the reels. Meanwhile, every time a book lands, it will fill out a progress bar on the left side of the reels. When the counter reaches 99, the bonus game will start.

Book of 99 Free Spins

You will initially get ten free spins. Before the spins start, a random symbol is chosen to represent the round’s special expanding symbol. When that symbol expands after appearing two (high-tier) or three (low-tier) times on the reels, it will pay out on all ten paylines according to its paytable value and the number of symbols. Before the symbols expand, all regular wins will be paid accordingly.

While all of this is going on, the progress bar will remain at the level it was on before free spins started. If you get three or more wild scatters during the round, you will get additional free spins.

What Is the Return to Player of Book of 99?

The theoretical RTP of this video slot is 99%, making it one of the few video slots with such a high return percentage.

What Do We Think of This Slot?

Book of 99 is worth playing just based on its RTP, but this is pretty much the only strong suit of the game, albeit a significant one.

The graphics and sound effects are okay for 2021. What’s more, this theme is a little bit overused in the video slot industry, so the game doesn’t really stand out in the visual department.

We liked that there are two ways to trigger the bonus round and that the game basically awards failed attempts at landing three or more scatters (it only takes one or two scatters to fill the progress bar). The bonus game itself is rather basic, but it can create some massive wins.


Book of 99

The maximum win in Book of 99 is 12,075x your bet.
Book of 99 is considered a high-variance slot, providing few but significant wins.
There is no option to purchase a bonus round in Book of 99, and even if it were, it wouldn’t be available on UK casino sites due to regulations.
Yes, if you wish to practise and see what this game is about, you can find it in free mode in many online casinos.
The official RTP of Book of 99 is a staggering 99%, hence the name.

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