, fan books
, and profile books
all fall under this category at our store here. These books do not contain parts of the story - instead, they are designed to accompany it. For example, any Bleach fan, whether they watch the anime or read the manga, can enjoy a separate book with extra information about all of the characters... Likewise, any Naruto fan can enjoy special artwork found in an art book.
Each and every fan book may have very different content than the previous one, so they're hard to summarize. In general, these books often contain character profiles, extra artwork, alternate stories, character ratings and polls, and in-depth explainations for various things about a particular anime or manga.