Book of 99 Slot Review

4.1/5
Based on our expert’s review. Reviewed by
Relax Gaming Slots
Review by
Chris Taylor
Updated: 13/10/2023
Review by
Chris Taylor
Updated: 13/10/2023

Battle the mighty Cyclops in the Book of 99 slot, an ancient Greek adventure from Relax Gaming. It’s a superbly designed 5 reel, 10 payline game that comes with a Free Spins feature where an expanding symbol fills the reel whenever it hits. This special symbol doesn’t have to appear on adjoining reels to trigger a win either. So far, so standard. What makes Book of 99 stand out is its massive 99% RTP rate. With 5,000 x bet max wins, find out more about this potentially game-changing slot with our Book of 99 demo and review.

Max Win
5,000 x bet
Play
T&Cs Apply

18+ new players only. Minimum deposit: £20. Maximum £100 bonus. Max bet with an active bonus: £2. Wagering requirement 100% match bonus: 30 times sum of deposit + bonus. Max redeemable from welcome bonus: £500. 100 Free Spins are given out 20 per day on Book of Dead for 5 days in a row, log in each day is required. Max Free Spins winnings: £100. Winnings from Free Spins are credited as bonus money with a wagering requirement of 45 times. Free Spins expire after 3 days. Some games may not be played with a bonus. Games may contribute differently when wagering a bonus. Play Responsibly! www.begambleaware.org. #ad

Provider
Relax Gaming
Type of Slot
Video Slot
Theme
Ancient Greek
Reels
5
Paylines
10
Stakes Range
10p to £100
Bonus Features
Yes (2)
Free Spins/Multiplier
10-Unlimited/1x
Max Win
5,000 x
RTP
99%
Volatility
Very High (5/5)

Book of 99 Demo

18plus uk-gambling-commission online-slot-co-uk-logo agechecked-verification-provider
T&Cs Apply 18+ new players only. Minimum deposit: £20. Maximum £100 bonus. Max bet with an active bonus: £2. Wagering requirement 100% match bonus: 30 times sum of deposit + bonus. Max redeemable from welcome bonus: £500. 100 Free Spins are given out 20 per day on Book of Dead for 5 days in a row, log in each day is required. Max Free Spins winnings: £100. Winnings from Free Spins are credited as bonus money with a wagering requirement of 45 times. Free Spins expire after 3 days. Some games may not be played with a bonus. Games may contribute differently when wagering a bonus. Play Responsibly! www.begambleaware.org. #ad
18plus uk-gambling-commission online-slot-co-uk-logo agechecked-verification-provider
T&Cs Apply 18+ new players only. Minimum deposit: £20. Maximum £100 bonus. Max bet with an active bonus: £2. Wagering requirement 100% match bonus: 30 times sum of deposit + bonus. Max redeemable from welcome bonus: £500. 100 Free Spins are given out 20 per day on Book of Dead for 5 days in a row, log in each day is required. Max Free Spins winnings: £100. Winnings from Free Spins are credited as bonus money with a wagering requirement of 45 times. Free Spins expire after 3 days. Some games may not be played with a bonus. Games may contribute differently when wagering a bonus. Play Responsibly! www.begambleaware.org. #ad

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Book of 99 Slot RTP, Details & Wager Limits

Reels/Paylines: 5 reels + 10 paylines

Stakes Range: 10p to £100 per spin

RTP: 99%

Max Win: 5,000 x bet per spin

The Book of 99 slot is played on a classic 5 reel, 3 row machine with 10 active paylines. To create a winning combination, land 3, 4 or 5 matching symbols or wilds from left to right on 1 of those paylines, starting from reel 1. With the 4 higher value symbols, only 2 (or more) are required in combination. Things are slightly different with the expanding symbols in the bonus feature which we’ll look at below.

Stake levels in range from 10p to £100 per spin thus catering to all players and pockets. Use the + and – tabs below the reels to set your desired stake. Non UK players can opt for Turbo Mode and Autoplay. The latter allows infinite autospins with optional loss, win and single-win limits.

As impressive as the design and gameplay are, what really makes Book of 99 stand out is the return to player rate. The Book of 99 RTP is 99%. That’s the best number I’ve seen from any online slot and much higher than you’ll find from most slots which usually hover around the 96% mark.

If the RTP rate is important to you, check out the slots with the highest RTP. The good news is that there is no other RTP version.

When it comes to variance, it’s high as you’d expect. It’s ranked as 5/5 by provider Relax Gaming. There’s a 29.83% hit frequency rate so nearly a third of spins will give you a winning combination (a win every 3.35 spins on average).

The Book of 99 max win is 5,000 x your total bet per spin. However, the max simulated win is 12,075 x your total bet which was surely achieved in the Free Spins feature as a whole. The best opportunities of winning big come in the free spins due to the expanding symbol. A screen full of Apollo symbols will result in the max payout.

Theme: head to ancient Greece and battle amongst the gods

Theme: Ancient Greek

High Value Symbol: Apollo

Compatibility: Mobile, Tablet, Desktop

book-of-99-slot-base-game

The Book of 99 slot has an ancient Greek theme. With terrific design, it features mythological characters such as the giant one-eyed Cyclopes.  You are taken to a battle amongst the gods. The comic book visuals are complemented by a rather haunting backing track that adds to the air of mystery.

Set against a rustic, night-time backdrop, the reels here are set within marble columns. There you’ll find A to 10 symbols in precious metals and embedded with gemstones.  They’re joined by a quartet of higher value symbols. There’s Lamia (a female daemon), cyclopes (the one-eyed monster) Pythia and Apollo. Apollo is the most rewarding symbol. Land 2, 3, 4 or 5 of these on a payline and you’ll win a payout equal to 1, 10, 100 or 500 x your total bet.

The Book symbol serves a dual role. It’s a wild that substitutes for all the standard symbols (apart from the expanding symbol in the bonus round). Landing 3 of them on the same spin triggers the Free Spins feature. Here’s a table highlighting payouts and functions for all Book of 99 symbols:

Symbol Payouts/Info
book-of-99-slot-10-symbol10 3, 4 or 5 = 0.5, 2.5 or 10 x bet
book-of-99-slot-j-symbolJ 3, 4 or 5 = 0.5, 2.5 or 10 x bet
book-of-99-slot-q-symbolQ 3, 4 or 5 = 0.5, 2.5 or 10 x bet
book-of-99-slot-k-symbolK 3, 4 or 5 = 0.5, 4 or 15 x bet
book-of-99-slot-a-symbolA 3, 4 or 5 = 0.5, 4 or 15 x bet
book-of-99-slot-lamia-symbolLamia 2, 3, 4 or 5 = 0.5, 3, 10 or 75 x bet
book-of-99-slot-cyclopes-symbolCyclopes 2, 3, 4 or 5 = 0.5, 3, 10 or 75 x bet
book-of-99-slot-pythia-symbolPythia 2, 3, 4 or 5 = 0.5, 4, 40 or 200 x bet
book-of-99-slot-apollo-symbolApollo 2, 3, 4 or 5 = 1, 10, 100 or 500 x bet
book-of-99-slot-book-wild-scatter-symbolBook Wild/Scatter Substitutes + triggers Free Spins feature

Book of 99 Mobile

book-of-99-mobile-slot

Released on the 4th of May 2021, Book of 99 is available to play on all devices including smartphones, tablets and computers. You’ll find the same classy design and simple gameplay in all versions. Most importantly, the 99% RTP is present and correct no matter what device you’re using.

Book of 99 Bonus Features

In the Book of 99 slot game, the gameplay is straightforward. Free spins with special expanding symbols are the main feature offering. Slightly unusually, there are 2 ways to trigger the free spins.

Free Spins feature

book-of-99-slot-free-spins-feature

Land 3 or more wild symbols on the same spin to activate the Free Spins feature. Your reward here is 10 free spins. Before the free spins begin, 1 of the standard symbols is picked at random. This will be the special expanding symbol for the whole of the feature.

On each free spin, a standard payout consideration is made. If a special symbol lands, it expands to fill the whole of the reel. In addition to standard payline wins, the special expanding symbol can pay out on all 10 paylines depending on how the symbols fall.

Winning combinations made up of the expanding symbol don’t have to be connected either. For example, expanding symbols on reels 1, 3 and 5 would result in a winning combination being formed in the free spins. Now, your max win depends on which symbol becomes the special expanding symbol:

Symbol(s) Max Win (Full Screen)
Q, J or 10 100 x bet
A or K 150 x bet
Cyclopes or Lamia 750 x bet
Pythia 2,000 x bet
Apollo 5,000 x bet

Now, landing 3 or more wild symbols will result in a retrigger and another 10 free spins. Like slots with a similar bonus feature, there’s no limit to how many free spins you can play with.

Collection feature

There’s a second way to trigger the Free Spins feature. Each time a wild symbol lands, it’s collected in a meter to the left of the reels. This is called the Collection feature.

With each wild, you’ll progress along a treasure map. When you have amassed 99 wilds, you’ll trigger the free spins. These come with the expanding symbol just like in a standard trigger. When you’ve played out your 10 free spins, the meter resets and you’ll start collecting wilds once again on a quest to reach 99.

Book of 99 Review Summary: it’s all about the 99% RTP

Ratings
Theme & Symbols








Sounds & Music








Bonus Features








RTP (99%)








Max Win (5,000 x)








Originality








I’ve played plenty of slots that come with free spins and an expanding symbol. Such as Book of Dead (Play ‘n GO) and Book of Ra Deluxe (Novomatic). Whilst the design may not be top-notch, the Book of 99 slot has all the elements you’d expect from a ‘Book of’ game. It has the added Collection feature which gives you an extra way to get into the free spins.

However, what sets the Book of 99 slot apart is the 99% RTP rate. You won’t find a better figure than that anywhere. 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 rate.

With that number standing at 99%, it becomes well worth considering if you enjoy the ancient theme. The key to big wins is to get a high value special expanding symbol in the free spins. This could be the difference of 100 or 5,000 x bet payouts per free spin. That said, the average win in the free spins is 68.8 x your total bet so bear that in mind. The max simulated win of 12,075 x bet is impressive.

Whether this will nudge other slot developers into inching up their RTP rates remains to be seen. However, some slot sites may not include Book of 99 in the wagering for their welcome bonuses or free spins due to the high RTP rate. That remains to be seen.

If you like ‘Book of’ slots, there are plenty to choose from. I quite like Nolimit City’s Book of Shadows which offers 30,338 x bet top payouts. Another option is Book of Sam by ELK Studios which comes with 10,000 x bet max wins as well as 3 Electric Treats.

Pros
  • 99% RTP rate
  • 2 ways to trigger free spins
  • 5,000 x bet max wins
Cons
  • Could do with more bonus features
  • Max win could be higher

Book of 99 FAQs

What is the Book of 99 RTP?

The Book of 99 RTP rate is 99%. Yes, you read that correctly, the return to player rate is an eye-popping 99%. You won’t find a better number than that anywhere.

What is the Book of 99 max win?

The biggest possible win from Book of 99 is 5,000 x your total bet. This can be achieved by filling the reels with the high value Apollo symbol. This becomes more probable in the free spins if it’s a special expanding symbol.

Are there any Book of 99 free spins?

Yes, the Free Spins feature is played by landing 3 wild books. With unlimited free spins up for grabs, you’ll benefit from a special expanding symbol which makes it easier to achieve the 5,000 x bet max win.

How does the Collection feature work?

Collect 99 wilds and you’ll trigger the free spins. Known as the Collection feature, it offers you another way to enter the all-important Free Spins feature with a special expanding symbol.

Is there a Book of 99 free play version?

Yes, you can play the Book of 99 demo here at Online-Slot.co.uk. This allows you to try this high RTP game on mobile, tablet and desktop devices.

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