I think I'm going to do a quick comparison of both Library Thing(LT) and Visual Bookshelf(VB) to give you an idea of the things I like and don't like about each and why. Both serve the function of allowing the user to keep a record of the things that he/she has read. As I said, I really like this. Not only does it keep me from acciddently repeating books (it's happened a couple of times that I've gotten a few chapters in to something and started to realize that I've already read it), but it helps, as I said above, me to rehash things I've read and jogs my memory about authors that I had forgotten. As far as the interface goes, VB has a much more polished look to it. Very clean and user friendly. LT is a little more visually rough around the edges. It kind of reminds me of the St. Pete Library's catalog, Polaris. Both of these are functional, but it looks like they were designed by book-people, not computer people. LT does allow the user to search for books in a number of ways, which I do really like. VB, unless I'm mistaken, just searches Amazon.com, while LT let's the user choose among hundreds of different databases. I also like that in LT, the user can "catalog" a book if he/she can't find it. VB allows for books to be added, but not in as detailed a format as LT. Both try to match a user's interests with those of users with similar collections. Both allow users to review items when they are added to the collection. The biggest differnce, I feel, is that VB is designed by computer people...by that I mean there is a way to also keep track of albums, restaurants, etc in the same format, in the same application. LT is clearly geared more for librarians, or bookish types. Both are excellent concepts, as they allow for readers to keep a collection, compare it with others, and get new ideas for further reading.
I'm not sure that I'll keep up with LT as much as I do with VB, mainly because VB is a part of Facebook, something that I interact with fairly frequently. Not to say that I'm going to immediately write LT off, but I may forget about it in a busy patch in which I don't get much reading done.