I love reading, therefore I love books, therefore I love Amazon, therefore I spend a lot of time online browsing for books which I'll probably never buy and if bought probably never read.
One thing I've realized a long time ago is that for some books (especially the controversial ones) the reviews provided by other readers are as valuable as the book itself.
A good example for that are all the reviews for The God Delusion by Richard Dawkins. I don't even think I need to read the book after reading many of the great reviews there.
Here's an example of a guy who provides many insightful reviews.
Of course reviews must be taken with a grain of salt as humans have an unbelievable capacity for being biased without realizing it.
Speaking of useless reviews, take a look at the ones by this guy who has apparently become an expert on providing reviews for books he never read and products he never bought. Some are actually funny!