The Book of Mazarbul was written to document the Dwarves return to Moria. The Fellowship of the Ring found the scorched, tattered remains of this book in the Chamber of Mazarbul, and Gandalf gave the book to Gimli. As far as I know, this is the only book that explicitly shows up in The Lord of the Rings, so it seemed reasonable to borrow the name to document my own Tolkien collecting endeavors. I hope some of you find it useful!