This item belongs to the Bookworm set. Collecting three items from this set will transform Isaac into Bookworm.
Notes
Hearts are proportionally more likely to be generated, with Red Hearts, Soul Hearts and Black Hearts each having a 1/9 chance of being chosen, the other 6/9 being distributed among the other categories.
Book of Virtues: Grants a random wisp based on one of the Seven Deadly Sins. The wisp spawned isn't linked to the pickup dropped.
Pride: a blue bomb wisp in the middle ring. When destroyed, a small homing bomb that deals normal troll bomb damage is spawned.
Greed: 3 yellow coin wisps in the outer ring. Their tears may petrify enemies like Midas' Touch.
Wrath: an orange bomb wisp in the middle ring, which fire flaming tears. They drop troll bombs when continuously firing, and leave a bomb pickup when they die.
Lust: a randomly colored pill wisp in the inner ring, with effects that are the same as Mom's Bottle of Pills wisps.
Gluttony: a heart wisp in the middle ring, with effects that are the same as Yum Heart wisps.
Sloth: a Bob's Head wisp in the middle ring. Their tears travel in an arc like Ipecac but don't always explode on impact. There is a small chance for an exploding tear.
The Book of Sin is a reference to the Seven Deadly Sins. Unlike other Book items, The Book of Sin doesn't appear to be based on a real book or scripture.
Gallery
3DS The icon of The Book of Sin as seen on the lower 3DS screen.
This item belongs to the 
Bookworm set. Collecting three items from this set will transform Isaac into Bookworm.
Hearts are proportionally more likely to be generated, with 
Red Hearts, 
Soul Hearts and 
Black Hearts each having a 1/9 chance of being chosen, the other 6/9 being distributed among the other categories.
Each category has a 1/7 chance of being chosen.
Dice Shard, 
Emergency Contact and 
Cracked Key.
Bone Heart
Rotten Heart
Eternal Heart
Gold Heart
Half Red Hearts, 
Half Soul Hearts and 
Blended Hearts cannot be generated.
Coins can be of any type, with higher value coins, including 
Lucky Pennies, and 
Sticky Nickels, being rarer.
Bombs and 
Keys will always be singular (unless Isaac has 
BOGO Bombs and/or 
Humbleing Bundle).
Micro Battery.
Book of Virtues: Grants a random wisp based on one of the Seven Deadly Sins. The wisp spawned isn't linked to the pickup dropped.
Pride: a blue bomb wisp in the middle ring. When destroyed, a small homing bomb that deals normal troll bomb damage is spawned.
Greed: 3 yellow coin wisps in the outer ring. Their tears may petrify enemies like 
Midas' Touch.
Wrath: an orange bomb wisp in the middle ring, which fire flaming tears. They drop troll bombs when continuously firing, and leave a bomb pickup when they die.
Envy: a white face-like wisp in the outer ring.
Lust: a randomly colored pill wisp in the inner ring, with effects that are the same as 
Mom's Bottle of Pills wisps.
Gluttony: a heart wisp in the middle ring, with effects that are the same as 
Yum Heart wisps.
Sloth: a Bob's Head wisp in the middle ring. Their tears travel in an arc like 
Ipecac but don't always explode on impact. There is a small chance for an exploding tear.
Books 
The Binding of Isaac: Rebirth
