book of 99

Battle the mighty Cyclops in the Book of 99 slot , which offers an ancient Greek adventure from Relax Gaming. It is a beautifully designed 5 reel, 10 payline game that comes with a free spins round where an expanding symbol fills the reel when it lands. This special symbol also does not need to appear on adjacent reels to generate a win. So far, it's pretty standard. What makes Book of 99 so special is the huge RTP percentage of 99%. Find out more about this potentially game-changing slot in our full slot review.

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Play Book Of 99 Slot Machine

This slot is played on a classic 5 reel , 3 row machine with 10 active paylines. To complete a winning combination you need to get 3, 4 or 5 matching symbols or wilds from left to right on 1 of those paylines, starting from reel 1. This is slightly different with the expanding symbols in the bonus feature which we will discuss below. see. Betting levels range from 10p to AUD100 per round to suit all players and wallets. Use the + and – tabs below the reels to set your desired bet.

As impressive as the design and gameplay are, what really makes Book of 99 stand out is the return to player rate. The RTP is namely 99%. That's the best figure we've ever seen from an online slot and much higher than most slots that usually hover around 96%. If the RTP percentage is important to you, check out the slots with the highest RTP.

When it comes to variance, this is as high as you would expect. The maximum win is 5,000 x your total bet per round. The best chances to win big can be found in the free spins round with the expanding symbol. There is a hit frequency of 29.83%, so almost a third of the spins will give you a winning combination.


This slot machine has an ancient Greek theme. With a great design, it features mythological characters such as the giant one-eyed Cyclops. The comic-like imagery is complemented by a rather spooky backing track that adds to the atmosphere of mystery.

The reels are set in marble columns against a rustic, nocturnal backdrop. There you will find A to 10 symbols in precious metals embedded with gems. They are joined by a quartet of higher value symbols. You will find Lamia (a female demon), Cyclopes (the one-eyed monster) and male and female characters here. The male hero is the highest paying symbol. Get 2, 3, 4 or 5 of these on a payline and you win a payout equal to 1, 10, 100 or 500 x your total bet.

The book symbol has a double role. It is a wild that substitutes for all standard symbols (except the expanding symbol in the bonus round). If you get 3 on the same spin, the Free Spins feature is activated.

Slot is available to play on all devices including smartphones, tablets and computers. You will find the same stylish design and simple gameplay in all versions. Most importantly though, the 99% RTP is present and correct no matter what kind of device you are using.

Bonus features

In this slot game the gameplay is straight forward. Free spins with special expanding symbols are the main feature. Somewhat uniquely there are 2 ways to trigger the free spins.

Free Spins

Get 3 or more wild symbols on the same spin to activate the Free Spins feature. Your reward is then 10 free spins. Before the free spins start, 1 of the standard symbols will be chosen at random. This will be the special expanding symbol for the entire feature.

On every free spin, a standard payout consideration is made. If a special symbol lands, it will expand to fill the entire reel. In addition to the standard payline wins, the special expanding symbol can pay out on all 10 paylines, depending on how the symbols land.

Winning combinations that contain the expanding symbol also do not have to be connected. For example, expanding symbols on reels 1, 3 and 5 result in a winning combination. Now getting 3 or more wild symbols will result in a retrigger and 10 more free spins. As with slots with a similar bonus feature, there is no limit to the number of free spins you can win.


There is a second way to activate the Free Spins feature. Every time a wild symbol lands, it will be collected in a meter on the left side of the reels. This is called the Collection feature.

Each wild will advance you past a treasure map. When you have collected 99 wilds, you activate the free spins. These come with the expanding symbol just like in a standard trigger. When you have played through your 10 free spins, the meter resets and you start collecting wilds again on a quest to reach 99.


We have of course played many slots with free spins and an expanding symbol. Such as Book of Dead (Play 'n GO) and Book of Ra Deluxe (Novomatic). While the design may not be top notch, it has all the elements you would expect from a 'Book of' game. It has the added Collection feature that gives you an extra way to get into the free spins. With its impressive sound and visuals and classic bonus feature, Book of 99 would be a perfectly playable slot if it had an average RTP percentage.

At 99%, it's definitely worth considering if you like the theme. The key to big wins is getting a special high value expanding symbol during the free spins. This can be the difference between 100 or 5,000 x your stake in terms of payouts per free spin.

Whether this will encourage other slot developers to increase their RTP percentages remains to be seen. However, some casinos may not include Book of 99 in the wagering for their welcome bonuses or free spins due to the high RTP percentage. That remains to be seen.

Frequently Asked Questions

What is the RTP?

This is 99% and therefore very high.

Which provider developed this slot?

Relax Gaming created the slot.

What is the maximum profit?

This is 5,000 times your stake.

Can I win free spins?

Yes, this can be done in two ways.

Is there a free version of this slot?

Yes, there is a demo version to try the game for free.

Written by: Jason Vink |

Jason is an online casino expert. He obtained a BA in Communications in Brussels before starting to work at internet gambling portals in Malta (EU) in 2012. He later joined and has since started sharing his expertise with our readers. Jason is able to assess and test an online casino on many different functionalities to ensure the enjoyment and safety. If you have questions for Jason, you can always send him an email: jason [at]