There may not be a single day that social networking concept does not extend to another level and improve another area of the drowning-in-content-overload humankind.

Here is two social networking sites that revolve around book-reading preferences of their members: LibraryThing and Shelfari.

If you experience the same problem while browsing Amazon – a vicious cycle of failures to decide which books to get, as there are way too many books with too few valuable comments -. Wouldn’t it be just great to get suggestions from other folks out there who read the same book two months ago? Now, that is the point where LibraryThing and Shelfari gets into business and provides you the interface to accomplish that mission.

[Let's also remember Suggestica [recently reviewed here], which lists reading lists of experts and famous business-persons.]
LibraryThing is older, has a deeper database and more users, which translates into more comments and reviews. Shelfari, on the other side, has graphically superior user interface, which makes browsing a lot funnier. My suggestion: use both and enjoy the next book coming out of these sites.