There is not another medium I know of that pushes the limits of human imagination via possibilities that provide perspective for our current trajectories. Here are some of the finest books I have read in terms of stimulating growth, if not approachability.
Dune - Frank Herbert
The Dispossessed - Ursula LeGuin
Lord of Light - Roger Zelazny
The Parable of the Sower - Octavia Butler
Hyperion - Dan Simmons
Oryx & Crake - Margaret Atwood
The Simulacra - Philip K Dick
Anathem - Neal Stephensen
The Moon is a Harsh Mistress - Robert Heinlein
1984 - George Orwell
The Foundation Triology - Isaac Asimov
Ender's Game - Orson Scott Card