True in principle, but I find in practice the Hugo and Nebula seldom disappoint me (in the sense of having wasted my time, not that every winner is a masterpiece). And these are not the only prizes (or genres), I just mentioned two. There are also magazines, reviews, etc. Sometimes following an author you like on Twitter or whatever helps see what they like.

Friend's recommendations aren't gamified. Actual friends I mean, not facebook contacts.

In any case, these were just examples that Amazon is NOT the place to go for browsing books. I'm sure people must do it, but I don't know of anyone who goes to Amazon to look for book recommendations...