These sprites were generated to be used as spellbooks in a roguelike game (Lore of Rune Era). The process for their generation is pretty straightforward — a series of image layers, each of which can have one or more possible sprite, are colored and drawn on top of each other. This allows for variation in the shape and details of the sprite — some of the books have different bookmarks or clasps, for example, and vary in color.
Each book is also given an icon for the cover, which is generated simply as a purely random (50% chance to be on or off) grid of pixels mirrored over the X and/or Y axis. Over the small size used here — just 5 x 7 pixels — this results in intentional-looking icons.
In the context of the game itself, the book sprites can be controlled to give a visual indication of their contents, so that a book of fire spells could be primarily red and orange, a book of healing spells could be white and gold, etc. My current work here is to extend this type of sprite generation to other types of items such as weapons, armor, and potions.