Hmm, have been pondering why I choose the books I do as a result of this.
The Slap (which I hated), I heard being discussed on R4 the week it came out and made a note to myself it was one I wanted to read. It turned up on a second hand stall about a year later and I bought it. It then sat on my bookshelf for several years until I got round to reading it. I hadn't heard loads of bad things about it before buying it. Once I'd bought it, I might as well read it! It sounded interesting in the original discussion, and I think it could have been, but he was more interested in making all the characters one-dimensional, quite nasty, caricatures and that completely drowned out the original idea.
50 shades - knew almost from the first I heard about it that it wouldn't be my thing so I won't bother.
I don't 'browse' on Amazon though. I go to Amazon to order a specific book I've heard about. (I listen to a lot of Radio 4, so might hear books reviewed on anything from Woman's Hour to A Good Read to Open Book!!). If I hear a review of a book I think is interesting, I go to Amazon and put it on my wishlist. My wishlist is currently over 500 items long.... Sometimes, I follow up some of the 'people who bought this also bought that' suggestions, especially for more obscure books (like lost classics) and if the blurb and comments sound interesting I'll stick that on the wishlist too.
At the moment, I've got well over 500 books at home that I haven't yet read. Somewhere in there, I will guarantee that there are books that got rave reviews when they came out that people since have dismissed as over-rated. By the time I get round to reading them, I'll have forgotten who said what and need to read them myself to see what I think!
I do keep an eye on best-sellers, but not indiscriminately -I know what kind of stuff I like and if the best-seller doesn't fit that, I don't bother, whatever anyone else says about it.