Book of 99 Slot (Relax Gaming)

The Book of 99 slot game has 5 reels, 3 rows and 10 fixed paylines. As simple as online slot games come, landing 3, 4 or 5 matching symbols across any payline, from left to right and beginning from the leftmost reel will reward you with a winning combination. For the highest-value symbols, 2 or more are needed. Finally, only the highest paying combination on each payline is awarded.

Regarding bet options, you can play Book of 99 from 10p to £100 a spin. You may find the maximum bet limited at some casino websites (£5 or £10 per spin) On a laptop or PC, use the plus and/or minus buttons to change your bet. On a tablet or smartphone, use the ‘Coins’ icon to adjust accordingly. Non-UK players have an Autoplay function (infinite auto spins with optional loss, win and single-win limits) as well as Turbo Mode (for faster spins).

The Book of 99 RTP rate is 99%. Well above the online slot game average of 96%, Relax Gaming has rewritten history with a first-of-its-kind RTP rate for a ‘Book of’ slot game. Furthermore, there are no other RTP versions as it would defeat the purpose of the game’s title.

Very high volatility, it’s classed as 5/5 on the variance front. Winning combinations will land every 3.35 spins on average as the hit frequency rate is 29.83%.

Lastly, the Book of 99 slot comes with 5,000 times bet max wins. This can be achieved on base game as well as free spins with a screen full of the highest-value symbol doing the trick. In the Free Spins feature though, where big wins are much more likely, the average win is 68.8 times your total bet.

Chris Taylor

The king of slots

Chris Taylor is an industry veteran originally from Gibraltar. Having worked in the online gambling industry since 2004, Chris loves slots and has reviewed over 10,000 online slot games. Running a slots-focused website for 13 years, Chris is the go-to guy for everything slots-related.

Released on the 4^th of May 2021, the Book of 99 slot has an ancient Greek-theme. In this Greek odyssey, you battle amongst the gods in this unique ‘Book of’ title.

With a cartoon-style design, you encounter mythological warriors. Set at night time, you’ll hear a harrowing soundtrack which sets the scene for the battle ahead. Marble columns encase the reels.

On the reels, you’ll encounter A, K, Q, J and 10 royals which all sport previous metals and gemstones. The higher-value symbols include the female daemon Lamia, the one-eyed monster Cyclopes, the high priestess Pythia and the God of the Sun and Light Apollo. 

Apollo is the best-paying symbol awarding 500 times your total bet for 5 across a payline. A screen full of Apollo symbols will result in a 5,000-times bet reward.

Finally, there is the Book Wild/Scatter symbol. Substituting for all symbols above, it’s the key to triggering the Free Spins feature. Below is a list of symbol payouts and functions:

• Q/J/10: 3, 4 or 5 = 0.5, 2.5 or 10 x bet
• A/K: 3, 4 or 5 = 0.5, 4 or 15 x bet
• Cyclopes/Lamia: 2, 3, 4 or 5 = 0.5, 3, 10 or 75 x bet
• Pythia: 2, 3, 4 or 5 = 0.5, 4, 40 or 200 x bet
• Apollo: 2, 3, 4 or 5 = 1, 10, 100 or 500 x bet
• Book Wild/Scatter: Substitutes for all symbols + triggers Free Spins feature

Book of 99 Mobile

Created with HTML5 technology, Book of 99 will detect whatever device you’re using and serve you the appropriate version. Compatible with laptop, PC, tablet and mobile devices, it can be played on iOS and Android smartphones. If playing on your mobile, there’s a Portrait Mode version which is vertical and occupies the whole screen.

The Book of 99 slot game has 2 bonus features. With the focus on the Free Spins feature, you get 10 free spins with a special expanding symbol. This randomly chosen symbol pays Scatter style. Relax Gaming has added a unique Collection element which gives you another way of triggering the free spins.

Free Spins

The Free Spins feature is triggered by landing 3 or more Book Wild/Scatter symbols on the same base game spin. With 10 free spins awarded, 1 of the symbols is chosen randomly to act as the special expanding symbol for the duration of the feature.

If the special expanding symbol lands, it will expand to fill the entire reel. The good news is that special expanding symbols don’t need to be connected from left to right across paylines. This means the expanded symbols pay Scatter style.

Your win potential depends on which symbol is chosen as the special expanding symbol. Getting Apollo makes it a lot easier to achieve 5,000 times bet max wins whereas the Q, J or 10 royals will lead to 100 times bet payouts if you fill the reels with them entirely. To achieve the max wins highlighted below, you would need that special expanding symbol to appear on all 5 reels during a free spin.

Look out for the Book Wild/Scatter symbol as 3 or more will reactivate the feature and reward you with 10 additional free spins, with no limits.

Book of 99 Slot

Rating: 4.2/5

Book of 99 is an Greek Mythology-themed slot with special expanding symbols during the free spins that can lead to 5,000 x bet max wins. Importantly, it boasts an unprecedented 99% RTP rate!

Chris Taylor

The Book of 99 slot may seem like another ‘Book of’ game but Relax Gaming has managed to release a first-of-its-kind 99% RTP slot. With an average of 96% for more slot games these days, the 99% RTP is extremely high and makes it one of the top RTP slots online.

In terms of the gameplay, the focus is fully on the Free Spins feature where 1 special expanding symbol is randomly chosen. Whilst the max win of 5,000 times your total bet can be won on base game spins (by filling the reels with Apollo symbols), it’s much more likely during the free spins (especially if Apollo is chosen as the special expanding symbol).

I like the fact that special expanding symbols don’t have to appear on adjacent reels to award a win (i.e. Scatter Pays). Relax Gaming has also added the Collection feature into the mix which gives you another way of triggering the free spins. That said, Relax hasn’t specified the RTP allocated to this feature.

Boasting 5,000 times bet max wins, Book of 99 can pay up to 12,075 times your total bet in the Free Spins feature as a whole. As mentioned above, the average win of 68.8 x bet in the feature is something to consider.

In summary, the Book of 99 slot is another ‘Book of’ game but with a very high RTP rate. Some casinos/slot sites will not allow this game to be part of a welcome offer or free spins promotion due to the return rate.

Book of 99 is another game in a long line of ‘Book of’ slots. Inspired clearly by the likes of Play ‘n GO’s Book of Dead and Novomatic’s Book of Ra Deluxe, our Slots Content Manager Jenny Mason compiled the top 10 ‘Book of’ slot games from the hundreds that are available to play online. Find out which ones made the list:

ALSO READ The Top 10 ‘Book of’ Slot Games

The Book of 99 slot review was written by Chris Taylor from our OLBG Expert team who has written over 10,000 slot game reviews in an iGaming career spanning over 2 decades. It was then verified/checked by Jenny Mason, our prime Slot reviewer who has 17+ years working in online gambling, top UK brands. 

Jenny Mason

Queen of bingo

Jenny Mason has more than 17 years of experience in the online gambling industry and has worked for some of the UK’s top betting brands. She started at OLBG in 2014, and her role involved creating great content and looking after marketing activities. Jenny is knowledgeable in all areas with specialisation in Bingo and Online Slots.