A few months ago someone recommended that I join Goodreads.com. I wasn't really convinced because usually when my friends recommend books to me I end up disappointed because I don't like them as much as they did. But after dealing with the creepy Amazon recommendation I've been struggling to find a new source for book reviews to recommend some books that I might not pick up otherwise.
I love that once you rate a book it gives you recommendations of books in similar categories. Like the "best books of 2007" or "best science fiction", however I have noticed that a) when you chose a category there seems to be a lot of books by the same author, so if you've tried some of their stuff and you don't like it well then the list is kind of a waste for you, and b)Many of the books end up in best and worst lists, take Twilight for example it appears in both "best books ever" and "worst books of all time".
I guess you just have to take the time to read the reviews to figure out if you think you'll like it.
Edit: Just took a look at the "Worst Books of all Time List", and while I'm not suprised there were A LOT of books by conservative authors. But being a conservative I've kind of gotten used to this sort of crap.