Ask HN: What are the best Sci-Fi books you've ever read? 8 years ago
I would recommend Ubik by Phillip K Dick.
It reads like a thriller and a mind bender. It sort of has the feel of the movie Inception if you liked that. It's not too long or hard to read, and it's completely self contained. The more I read by Phillip K Dick the more I appreciate his ideas.
I also second a recommendation for A Player of Games someone noted above.