Book of 99 Slot

Relax Gaming - Book of 99

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Book of 99 Online Slot Review

Relax Gaming has created a slot that combines two of the most popular themes in slots nowadays, the "Book of…" and the Ancient Greece theme. Such a combination means nothing but success since the Book of 99 slot is about to make a real boom across the industry.

You may not assume from the title right away, but the title is related to the mind-blowing RTP this game offers. Book of 99 offers a staggering 99.00% RTP, and that’s its strongest suit, and one of the main differences between it and its Play'n GO's counterpart – the Book of Dead slot. Add to that the fact that the highly volatile slot comes with a pretty standard 10-payline, 5 reels grid, and you’ve got yourself an already exciting slot to play. But, you should know that you’ll be showered with Free Spins and Expanding Symbols, as well as the Wild Collection feature, taking you to wins of up to 12,070x the stake. Ready to explore the Greek temples and meet the villains and heroes of the glory Ancient Greece days?

Book of 99 Game Logo
RTP 99.00%
Volatility High
Maximum Win €1,207,000.00
Bonus Buy Icon Error No
Game Provider Relax Gaming

Licensing Authorities and Testing Agencies

Book of 99 Slot Controls, Setup and Paytable

As mentioned, when you load the Book of 99 slot, you will be both mesmerized and creeped out by the symbol design. Relax Gaming has done an outstanding job creating the symbols, using cartoonish graphics, yet designing them to leave you in awe. They are both scary and beautifully designed, so you can rest assured that you'll enjoy the slot, in terms of visual effects.

When it comes to the setup and controls, the reels are at the center of the screen, presented on the wall of the temple. On the left side of the reels, on the temple’s pillar, you have the Wild Collecting Meter. On the right side of the reels, you see controls. First is the Quickspin button, followed by the bet configuration field, where you can place a bet from 0.10 to 100 credits. The Play and Autoplay buttons are next.

Next, you see the three-bar button, where the paytable is. You will see that the low-paying symbols are the playing card Royals, in Greek style, while the high-paying are characters, villains and heroes, from the ancient Greek stories. The high-paying symbols can deliver payouts from 75x to 500x the stake.

Finally, below the reels, going right to left, you see the Bet display, the Win display and the Balance display.

Book of 99 Mobile Slot

Relax Gaming always makes sure you get to play its free slots across all devices. To do that, it uses the HTML5 format for all of its slots, making them playable across all Android and iOS devices.

Therefore, regardless of whether you have a Samsung or an iPhone, or any other smartphone or tablet, you can rest assured that Book of 99 will play interruption-free on any device.

Reels 5
Rows 3
Autoplay Option
Autoplay Option Icon Yes
Release Date
Release Date 04/05/2021
Paylines 10
Minimum Bet
Minimum Bet €0.10
Maximum Bet
Maximum Bet €100.00

Book of 99 Slot Base Game Features

There are a few things you need to know about the base game of Book of 99. The Book symbol is the Wild, which substitutes for all symbols bar the special Expanding Symbol during the bonus game. There's much, much more to this slot machine than the free spins bonus though.

You should also know that any time you land this symbol, it gets collected on the left side of the reels, in the Wild Collection Meter. Collecting 99 Wilds, you will trigger the bonus game. Should you trigger the bonus game this way, it will be played with a bet size corresponding to the average of the bet sizes used when collecting each Wild.

Book of 99 Slot Free Spins and Bonus Features

While you can trigger the Book of 99 bonus game by collecting 99 Wilds, you can also trigger it the easier way. You can trigger it by landing 3 or more Wilds, from left to right on adjacent reels, for which you get 10 Free Spins. So essentially, the Wild Collection feature will help you later retrigger the feature, since you’ll need time until you collect 99 Wilds, compared to landing only 3 or more Wilds to first trigger the bonus game.

Before the Free Spins start, the game will select a random symbol to become the special Expanding Symbol, much like in the classing Book of Dead online slot. Land the Expanding Symbol, and it will expand to cover the entire reel it landed on. Land more than one Expanding Symbol, and they will pay both ways, regardless of the lines they landed on, even if the symbols are not connected from left to right.

Slot Features

Scatters Icon Yes
Wild Symbol Icon Yes
Free Spins Icon Yes
Stacked Symbols Icon Yes
Quickspin Icon Yes
Retriggering Icon Yes

Book of 99 Slot RTP, Max Payout & Volatility

The most important part of the Book of 99 real money slot is that it comes with an incredible 99.00% RTP. It cannot be stressed enough how important this is, since the slot will deliver a Return to Player percentage of 99.00%.

Add to that the fact that the slot arrives with a max payout potential of 12,000x the stake, and you’ve got yourself a winner! For the max bet of 100 credits, Book of 99 can deliver 1,207,000 credits! That’s right, it can make you a millionaire in a blink of an eye!

Book of 99 Slot Verdict

Book of 99 is an incredibly unique slot, truly worth the try. Its title does remind you of Book of Ra, but the slot is nothing like it. The design does remind you of the old Medusa series of slots. Relax Gaming has done an amazing job with the overall production. Yet, the star of the slot is the 99.00% RTP. This RTP is rarely offered by developers nowadays, so it is quite a refreshment. This 99.00% RTP paired with the 12,070x the stake max payout potential make Book of 99 the it-slot, the slot that could well become the next big thing. You can try it out at one of our best online slot sites for real money!

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Meet Our Slot Tester

Karolis Matulis
Karolis Matulis Slot Tester

Karolis Matulis is an SEO Content Editor at with more than 5 years of experience in the online gambling industry. Karolis has written and edited dozens of slot and casino reviews and has played and tested thousands of online slot games. So if there's a new slot title coming out soon, you better know it – Karolis has already tried it.

This review is based on the writer's personal opinion is an informative comparison site that helps users find the best products and offers. We maintain a free service by receiving advertising fees from the brands we review. Ratings are based on position in the comparison table or specific formulas. We strive to keep information up-to-date, but offers are subject to change. We do not compare or include all brands and offers.


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