Book Of Diamonds: review, 96.14% RTP and up to 5000× max win

Book of Diamonds is a Spinomenal five-reel game with 10 paylines, a 5000× ceiling and — unusually — a studio that publishes every RTP setting it ships. Its own pitch promises “rare diamonds and fruits” and “a fest of colors, features and epic wins”. The spec sheet underneath is more useful than the pitch, so that is where this review starts.

⚠️ Four RTP settings, and seven points between them

Spinomenal’s spec sheet lists four configurations:

Setting	Return
96.14%	the best build
93.96%	two points worse
91.71%	four and a half points worse
88.94%	seven points worse

The operator chooses. Nothing in the game’s appearance changes between builds, and 88.94% is a long way below what a player would assume from the headline figure. Credit where it is due: most studios publish only their best number; Spinomenal publishes the whole list, which is what lets you check.

Is Book of Diamonds worth playing?

On the 96.14% build, it is a reasonable ten-line game with a 5000× ceiling. On the 88.94% build, it is not — and that single fact matters more than anything the features can do.

What we can say beyond that is limited, and we would rather be explicit about it:

• Volatility: Spinomenal does not publish it, so our spec card leaves it empty.
• Release date: not on the spec sheet.
• Demo: we have no playable source for this game yet, so we have not seen the features in action.

Verdict: worth a look only after you have confirmed the RTP setting in your casino. On anything below 93.96%, there are better ten-line games with published maths.

What the studio lists

From Spinomenal’s feature list: free spins, a bonus game, a scattered wild, expanding symbols and a buy feature.

That is the recognisable “Book of” format — a book symbol that works as both wild and scatter, and one symbol chosen to expand across the reels in free spins. It is a fair reading of the list, but Spinomenal does not describe how the features combine, and without a demo we have not verified it. The buy feature is only available where the operator’s market allows bonus purchases.

Bankroll tips

• Check the RTP line first. With four builds and a seven-point spread, it is the most important number in the game.
• Treat the 5000× as a ceiling, not a target. Ten-line games spread their value thin between features.
• Try it where a free mode exists before staking real money — we will add the demo here when we have a source for it.