There are many options out there (Goodreads, Shelfari, Google Books, Anobii, WeRead), including some good ones for sharing only with Facebook friends.
About 20min research leads me to believe that the best of the bunch is LibraryThing.
Check it out at librarything.com.
Sadly, I still find LibraryThing too crude. Having no widget for this WordPress.com blog is a deal breaker. … I’ll wait until something better comes along.
Leave a comment if I’m missing the perfect social network for books.
I saw a number of warnings about one competitor, now owned by Amazon – Shelfari. … Avoid.