An application to manage books you want to buy or have already read. Very handy if you're in a bookstore and don't remember which one's missing in your collection.
You can not only enter name of author, booktitle, category, series, publisher and condition, but also a long note for each book. You can filter the list views by category or series.
If you lend books, you can manage them too: you can record the due date and other lending related items and set an alarm in your datebook, so you don't forget to bring the book back.