When I can't find a book from a favorite author then I tend to buy based on the blurb. If the story sounds interesting then I'll give it a try. I've found new to me authors that way. Covers also grab my attention, but if the back cover copy isn't interesting then I'll pass. I have read reviews on books that I was waffling on to get a general sense of how the book will be. However, I do also look at other books the reviewer has reviewed, especially if the review is harsh and negative. It helps to see what types of book the reviewer does like, then I can usually determine if the reviewers review is worth considering.
I once had a reviewer who absolutely hated the book of mine she'd read. I think this reviewer would have given me a -10 if she could. Her wording was harsh, negative and became a personal attack, calling me uneducated and ignorant (redundant much?).
So I checked all her reviews to see what types of books she did like and had to laugh when I saw she was very much into Wicca and Witchcraft. Well, no wonder she didn't like my book its so the opposite of her preferences.