At Amazon I've just typed in the name of a book that I liked and seen what else comes up. More often than not I'm not getting the connection. It's almost like I'd read a different book.
I wonder if the books it brings up for me are based on some average between me and Mo since I use the same account to order for both of us. Maybe it thinks I'm a 30 year old with an interest in social studies and zombies.
That may well be a key!
I often find Amazon recommendations interesting and sometimes helpful.
But that's different from the "people who bought this" function....which I also often pursue for fun.
The Amazon recommendations can be affected by you if you go to fix this recommendation. You'll find out why they recommended it and you can tell them not to recommend things based on that purchase.