Books people wrote
Minecraft added writable books in 2012, and TWiTcraft's players used them for everything: a 31-page guide to the server's markets, a rule book for a Nether colony, shop flyers, job applications, a mailbox receipt, journals of exploration, a memorial for a dog, autographs, and at least one fifty-page prank. This is all of it that survived — every unique text found in a chest, an item frame, an inventory or an ender chest across the archived worlds, with the formatting the authors used.
A signed book is a finished "written book"; an unsigned one is a book-and-quill still open for editing when the server stopped. Nothing is left out or edited — these are public game files, and anyone can walk into the archive server and open the same chests. Only keyboard-mash test books are filtered.