With BookDB2 you can enter all your books with author, category, publisher etc and print them out in a variety of formats. Why would you need such a thing? Well, if you're always going to book sales and buying bargains only to get home and find you've doubled up, take a printout with you! BookDB2 has a super-condensed print mode so you'll need a magnifying glass, but at least it'll save a tree or two.
BookDB2 also has lending library features. With them, you can add borrowers, loan out books, add multiple copies and so on.