Mostly forums.
Such as:
A Song of Ice and Fire (Powered by Invision Power Board) There is a general literature subforum.
sffworld.com
Then I check Amazon's reviews but very carefully. People who reviewed only 1-3 items are ignored.
Goodreads is quite good too and it is free as opposed to Librarything where you can add only the first 200 books for free, after that you have to pay.