Book of Oil: free spins, bonuses and all the slot features

Book of Oil is a video slot from Endorphina, made in the classic "Book of..." format, but with a modern oil theme. The game uses 5 reels, 3 rows, and 10 paylines. The key feature is the Free Games bonus with expanding symbols.

The theoretical return to player (RTP) in the main game is 96.05%. When using the Bonus Pop Buy feature, the RTP varies between 94.73% and 95.98%, depending on the option selected. The minimum total bet is $0.10, and the maximum is $35.00. Only US dollars are used in the text.

Play Book of Oil online

Exclusive Book of Oil bonus for new players

Book of Oil Game Plot

The Book of Oil online slot transports players to the world of the oil business and big money. Symbols of drilling rigs, barrels of oil, and stacks of dollars form winning combinations, and the main goal is to activate bonus spins, where one symbol gains the ability to expand and bring large payouts.

Book of Oil game rules

Basic rules:

• Slot: 5 reels × 3 rows.
• Number of paylines: 10.
• All winnings are paid for combinations of identical symbols.
• Combinations are counted from left to right, starting from the left reel.
• All symbols except Scatter must be on active lines and adjacent reels.
• Scatter symbols are counted in any position on the reels.
• Only the maximum win is paid per line and for Scatter.
• Line wins and Scatter wins are added together.

Basic slot parameters

Parameter	Value
Provider	Endorphina
Game field	5×3
Paylines	10
RTP	96.05
Minimum bet	$0.10
Maximum bet	$35.00
Bonus	10 Free Games + expanding symbols

Symbols and payouts

High-paying symbols

• Businessman — up to 5,000x for 5 symbols.
• Oil rig — up to 2,000x.
• Oil barrels — up to 750x.
• Wads of cash — up to 750x.

Card symbols

The game uses standard symbols A, K, Q, J, 10, which form frequent but less profitable combinations.

Scatter and Wild

• The book acts as both a Scatter and a Wild.
• Wild replaces most symbols to form wins.
• 3 or more Scatters activate 10 Free Games.

Free Games with expanding symbols

Bonus activation

• 3+ Scatters trigger 10 free spins.
• Free Games can be re-won during the bonus.
• The bonus is played at the same bet and lines as the main spin.

Expanding symbols mechanics

• At the start of the bonus, one random symbol is selected.
• If there are enough symbols of this type to form a win, they expand vertically.
• The expansion occurs after the regular payouts have been calculated.
• Expanded symbols can pay even on non-adjacent reels on active lines.
• During Free Games, Wild cannot replace the special expanding symbol.

Bonus Pop Buy Feature

The Bonus Pop Buy feature allows you to buy Free Games at any time. Unlike the standard bonus, the player can choose the symbol that will expand during free spins.

• The cost depends on the total bet and the option selected.
• The bonus starts with a guaranteed appearance of 3 Scatters.
• Winnings from Bonus Pop cannot be used in the Risk Game.
• The feature may not be available at some operators.

Risk Game (Gamble)

After any win, the player can activate the Risk Game to try to double the payout.

• Choose one of four face-down cards.
• Beating the dealer doubles the winnings.
• Maximum of 10 attempts.
• Losing to the dealer means losing your winnings.
• The average RTP of the risk game is 84%.

Advantages and disadvantages of Book of Oil

Advantages

• RTP 96.05
• Expanding symbols in the Free Game
• Option to purchase Bonus Pop

Disadvantages

• High volatility
• Only 10 paylines
• Risk Game not available for Bonus Pop

Play Book of Oil for free

To familiarize yourself with the mechanics, the slot is available in demo mode. The free version allows you to learn the rules, bonuses, and behavior of expanding symbols without risking your balance.

Frequently asked questions about the Book of Oil slot

Play Book of Oil online