Logan's Run. That you game devs have not made something derivative of the original book (not the movie, the movie was as much like the book as World War Z was like that Brad Pitt fiasco) is a real crime. The book has deep issues on the table and plenty of twisted action.

OK then, also read World War Z.

Soon I Will Be Invincible

and...

Starship Troopers.

The entirety of the The Hitchhiker's Guide "trilogy" (all six books), by Douglas Adams and Eoin Colfer. They are some of my favorite sci-fi comedy books. Really hilarious!

Other authors I enjoy:

C.S. Lewis

Isaac Asimov

Arthur C. Clarke

J.R.R. Tolkien