I’m using LibraryThing, after fleeing GoodReads a few years back, and I just learned about BookWyrm. I’m interested in what others apps and sites are out there for keeping track of your books and/or to-read list, and/or reviewing and/or discussing them, and what folks think about them.
I’m using LibraryThing because of all the books listed (including the ability to add new books) as well as their early reviewers program (I’ve gotten a number of good books from that).
While I also have accounts on Goodreads and BookWyrm, right now I only use them to add books I’ve read and leave a review.