Check out the reviews on
Diablo 3
Is it a good game? Dunno, 'cos most of the reviews are penned by angry teens who can't log-in. Is that part of the gaming experience? You decide. (Whats great though is the angry reaction to the DRM system. Being forced to play online even when playing SP is pissing people off...)
While the above doesn't have much to do with books, the same principles apply. Expectations, poor formatting, etc...all affect reviewers and some people give them more weight than others.
You're still better off listening to friends + critics who have the same taste as you than with Amazon.