Book of 99 is a Relax Gaming book style slot released in 2021, set in a world of Greek gods. Its standout point is a 99% RTP, one of the highest published for any online slot. The rest of the game follows the familiar book format: 10 paylines, a wild that doubles as a scatter, and free spins with an expanding symbol. It suits players who like classic book slots and want the best possible return on paper.
How does Book of 99 work?
You play on five reels and three rows with 10 paylines. The Book symbol is both wild and scatter: it substitutes for regular symbols and also counts towards the free spins trigger.
There is a second way to reach the bonus. The game keeps a counter of every Book symbol you land, and when it reaches 99, the free spins are awarded. This means even a long run without three books still builds towards something.
What are the Book of 99 bonus features?
Landing three Book symbols, or filling the 99 Book counter, starts 10 free spins. Before the round begins, one symbol is chosen at random as the special expanding symbol.
During free spins, when the special symbol lands on enough reels to form a win, it expands to cover each reel it appears on and pays across all lines, even if the positions are not adjacent. A high paying symbol chosen as the expander is where the biggest wins come from, and the top payout of 12,075x is only available during the free spins.
The feature is simple compared to modern bonus rounds, which is part of the appeal for fans of the book genre. There are no extra modifiers to learn, so you can follow exactly why each spin paid what it did.
Is Book of 99 worth playing? RTP and volatility explained
The 99% RTP is the main reason to look at this game. It means that over a very large number of spins, the theoretical return is higher than almost any other slot. In a short session, though, results still swing widely because volatility is rated very high.
Casinos can choose to run lower RTP settings on many Relax Gaming titles, so the 99% figure is only meaningful if your casino uses it. Check the game rules screen to confirm.
Tips before you play Book of 99
- Confirm in the game info that your casino runs the 99% RTP version.
- Keep in mind that a high RTP does not prevent long losing streaks on a very high volatility game.
- Watch the Book counter; you may be closer to the guaranteed trigger than you think.
- Start with the demo to see how often the expanding symbol lines up.
- Note that the maximum bet is lower than on many slots, so the game suits smaller and mid sized stakes.