Book of 99

Book of 99 is Relax Gaming’s high-RTP take on the familiar book-slot format. It combines a published 99% theoretical return with expanding-symbol free spins and a maximum win cap of 5,000x stake. The headline RTP is useful for comparison, but it remains a long-run theoretical figure and does not predict the result of a spin or a short session.

How Book of 99 plays

The game follows a classic reel-and-payline structure, with the book symbol acting as both wild and scatter. Three or more books trigger 10 free spins. At the start of the feature, one of four character symbols is selected as the special expanding symbol. When enough copies land in view, that symbol can expand across the reels and create wins without needing to appear on an ordinary line in the same way as the base game.

Landing three books during free spins retriggers the feature. Relax Gaming also highlights a rare 99-book route into the bonus. The game launched on May 4, 2021, with Greek-mythology artwork and a deliberately direct variation on an established slot format.

RTP and reference stakes

Relax Gaming publishes 99% as the game’s RTP and lists a reference stake range from 0.10 to 100 in the currency used by its product page. That figure is a provider baseline, not proof that every operator serves the same configuration or currency limits. Players should open the information panel in the version they are using and confirm its displayed RTP and total stake before play.

The maximum win is 5,000x stake. As with any published cap, it describes the upper limit rather than the chance of reaching it. The combination of a high theoretical return and a conventional book feature is the real comparison point; neither factor removes normal slot variance.

Who it suits

Book of 99 is most relevant to value-conscious players who want an official provider-published RTP and familiar free-spin rules. It also suits classic book-slot fans who prefer one selected expanding symbol over a large tree of unrelated bonus modes. Players seeking clusters, hold-and-win respins, or a progressive jackpot should compare other mechanics. The demo can explain the feature flow, but only the paytable in the active operator build can confirm the exact configuration in use.