The books in Kisaragi Library were not properly categorized by type, perhaps to make the "readers" task more challenging. When Reno saw a few "Lost Dreams of the Red Chamber", "Rural common disease prevention and treatment guidelines", "Advanced Mathematics" and all other books arranged in a jumble, he already gave up on the idea of searching the books by type.
Even though the books were not classified by types, the shelves were sorted by the 26 letters of the English alphabet. They were hiding within the "W" section, between bookshelves 27 and 28 in the many bookshelves under that letter.
At the start, none of them could fully grasp the concept of "millions of books" mentioned in the rules. Once a number is too huge, its true meaning is hard to process, making it hard for people to get a proper impression of the numbers.
