With reviews, you're always taking a chance. If there are lots of reviews, it's most likely that the reviews haven't been orchestrated. However, you're also assuming that all the reviewers have the same opinion as you do. There really is no magic way of finding the perfect book. Over time, you'll likely find individuals who's reviews tend to work best for you. You should probably check with various sources if you can.
Other than that, you're always taking a chance with any reviews
Any book that only has one or two reviews are always risky as they could be rigged.
However, there have been very few books that I've disliked so much I regret buying them
