Bookllet

Bookllets are sentient book enemies that slowly float towards the player, occasionally firing bullets towards the player in various patterns resembling letters of the alphabet. The attacks are as follow:
 * Summons an R shaped string of bullets which then rapidly fire after the player one by one.
 * Summons an N which briefly stays in place before all the bullets that compose it fire directly at the player simultaneously.
 * Summons a Φ symbol which briefly stays in place before all the bullets that compose it shoot off in all directions.

Blue Bookllet
Blue Bookllets behave similarly to regular Bookllets, but have an additional attack that fires a ring of bullets that pulse back and forth. Blue Bookllets tend to be less common than normal Bookllets.

Green Bookllet
Green Bookllets behave similarly to regular Bookllets, but have an additional attack that fires bullets in all directions in a clover shape. Green Bookllets seem to be the rarest out of the variants.

Trivia

 * The letters that Bookllets use as attacks resemble the letters N, R, and Φ, which are the same as the hitmarkers that Gunther and Witch Pistol leave on walls and tables when shooting them.
 * The Φ bullet attack could possibly be a reference to the Phyrexian mana symbol from the trading card game Magic: The Gathering.
 * Blasphemy can be used to destroy the Bookllet’s letters or shapes before they are fired.