Wild Function
The Book substitutes for all symbols except — unusually — itself. When it appears on the reels during the base game or free spins, it completes adjacent symbol sequences on active paylines. For example: Rich Wilde | Book | Rich Wilde | Rich Wilde | Rich Wilde on payline 1 = a 4-of-a-kind Rich Wilde win (pays 100x). Without the Book wild it would be a losing combination. The Book wild also forms its own winning combinations — 5 Book wilds on a payline pays 200x stake.
Scatter Function
As a scatter, the Book pays regardless of payline position. Land 3 anywhere across the 5 reels in a single spin: 10 free spins triggered. Land 4: still 10 free spins but the trigger was less probable — not more spins. Land 5 scattered anywhere: still 10 free spins, but the scatter combination itself pays 20x your total stake as an additional win. The scatter payout for 3 Books is 0.2x stake; for 4 Books it is 2x stake.
During Free Spins
The Book scatter retains its triggering function during free spins. Landing 3+ Book symbols during the bonus round awards 10 additional free spins (retrigger). These stack with your remaining spins. The expanding symbol selected at the start of free spins continues to apply through all retriggered spins.
Why It Is the Game's Key Symbol
No other single symbol in the game's design carries this much function. The Book drives the base game through wild substitutions, triggers the primary bonus feature as scatter, pays scatter wins independent of paylines, and retriggers the bonus. Understanding the Book symbol — when it helps as a wild vs when it would be more valuable as a scatter — is the core of understanding what makes Book of Dead tick.