Book of 99

(Relax Gaming) Slot Review

Pragmatic Play

✅ Book of 99 Demo & Casinos


150% up to $3000
Up to 25% Rakeback

18+ | Terms Apply | Play Responsibly

bc game

€20k / $20k / 200 000kr
Buy crypto on the casino!

18+ | Terms Apply | Play Responsibly


5 BTC / €2k / $2k Bonus
Up to 60% rakeback

18+ | Terms Apply | Play Responsibly


€1500 / $1500 / 15 000kr
7500 free spins

18+ | Terms Apply | Play Responsibly

Book of 99: Slot Overview

To stand out in the unstoppable deluge of slots, designers really have to do something special. Maybe pick an unusual theme, jack the potential, or put thinking caps on to come up with trailblazing features no one has seen before. Developer Relax Gaming has chosen to do none of these things. As you can deduct from the title, Book of 99 is another 'book of' style game – this time set in Ancient Greece. Even potential is pretty standard for this type of game. What they've done, though, is attach an eye-catching RTP value that relates to the title, as well as add a generous collection system.

book of 99 slot

Book of 99 is also a nice game to look at, maybe not quite so much in the base game, but the bonus game plays in a sun-drenched easy on the eyes arcadia. There's a definite Relax feel to the rest of the game too via the cartoonishly designed symbols depicting various heroes and villains from the old glory days. Some are downright creepy (looking at you scary lady). The music is nice too, composed of a throbbing beat and a melody which adds a touch of exoticism to the proceedings.

Highly volatile, the Greco action takes place on a classic 'book of' reel set made out of 5 reels and 10 fixed paylines. Stakes may be set from 10 p/c at the lower end, rising to $/€100 for higher rollers, on any device. The unique selling point around here is the game's RTP configuration. Rarely do we see figures so high, and Relax bucks the downward trend by blessing Book of 99 with 99% RTP. Call it what you like – a gimmick, a trick to pull in punters; at the end of the day, it's a stellar value, making Book of 99 head and shoulders more desirable than many in the 'book' category.

Starting from reel 1, winning combinations are formed when matching symbols sit adjacently to each other on a payline. In this Greek odyssey, you'll find a group of attractive 10-A symbols at the lower end of things and higher-paying symbols, including a child-eating monster named Lamia, a cyclops, plus female and male leads. Low pays need at least 3 to make a winning combo, while high pays dish out coins for 2 or more. Should a line of 5 premium symbols line up, players collect a win worth 75 to 500 times their stake, making full screen wins particularly thrilling.

Book of 99: Slot Features

Book fans will certainly know the drill by now and Book of 99 sticks close to the template laid down many moons ago by Book of Ra. The central feature is expanding symbols in free spins, yet Relax Gaming has added a collection system you rarely find in these types of games.

As ever, the book symbol is the one you need to open up the game's best moments. It is wild, replacing pay symbols to complete win lines and the scatter - 3 or more in view award 10 free spins but no side payment, which is a little unusual. Before free spins launch, one of the pay symbols is randomly selected to be the special expanding symbol throughout the whole feature.

On each spin, special symbols expand to cover all of the positions on their respective reel after any regular wins have been paid. Expanded symbols pay-all-ways, from any reel, so they do not need to be next to each other or sit on reel one. Full-screen wins are the ultimate goal here - the more valuable the symbol, the better. One last point about free spins is they are retriggered when 3 or more book symbols land.

Lastly, let's look at the less orthodox feature - a wild collection system. For every wild symbol landed in the main game, a collection meter on the side of the screen increases by 1 step. Filling the meter with 99 collected wilds awards 10 free spins. Triggering the bonus round this way operates under the same rules, so those all-important expanding symbols come into play.

Book of 99: Slot Verdict

Book slots might be a dime a dozen, but Relax's contribution to this preeminent slot category comes with several convincing reasons why you would choose this over its competitors. RTP is obviously one of the main reasons, making Book of 99 one of the most generous slots out there. As a go-to for powering through a wagering requirement, it's hard to think of a better option. Book of 99 would be a great way to maximise your chances of getting returns in this situation - whether operators will play ball and offer it up for this purpose will be interesting to see.

Aside from its unusually high RTP, Book of 99 is a high quality 'book of' slot in its own right. For one, it looks nice, and the wild collection system is an extra sweetener on top. It adds a sense of purpose as well as a reward for persistent players. Even if getting 3 scatters to appear simultaneously is a chore, eventually, 99 of them will pass by, leading to free spins. That also raises the question, how much of that RTP is allocated to the base game and free spins respectively? Is the exceptionally high RTP a blessing or a curse? There's always a risk that wading through long base game sessions will eventually start turning into a chore. Part of what has made Book of Dead so successful, is its perfectly balanced math model.

At the end of the day, higher than normal RTP, plus a wild collection feature, makes Book of 99 a well-designed, attractive entry in the bloated 'book' market. Once again, it seems reinventing the wheel isn't a requirement for making a decent slot – provided there is an expanding special symbol in there somewhere.


For players confused over which ‘book of’ slot to pick, Book of 99’s epic RTP and extra free spins collection system make very compelling arguments.

Latest Reviews

Relax Gaming
Atlantis Crush slot

Atlantis Crush

Hungry Bear
Big Top Terror slot

Big Top Terror

Play'n GO
Whispering Winds slot

Whispering Winds

Notify of
Most Voted
Newest Oldest
Inline Feedbacks
View all comments