There was a time where Amazon was great to explore books: "users who bought also bought". Good old collaborative filtering. I feel bad for giving useless advic

There was a time where Amazon was great to explore books: "users who bought also bought". Good old collaborative filtering. I feel bad for giving useless advice so as someone who read several times the whole foundation series as a teen may I suggest: A deepness in the sky, a fire upon the deep, the forever war, gateway (Frederick Pohl). If you like fantasy, or even if not: the blade itself. If you have an enemy recommend him/her "the name of the wind". It's a great book but it's the first of an unfinished trilogy. Edit: how could I forget the cryptonomicon?