I've never used LibraryThing or LibraryElf, but I really like Goodreads - www.goodreads.com You can enter your books, write reviews, rate the books, add friends and read what they are reading and their ratings/reviews. They start you out automatically with 3 "bookshelves" Have Read, Am Reading, and To Read. But you can add as many bookshelves (categories, really) and name them whatever you wish.
Just an idea!