Superhuman: Slan by A.E. Van Vogt More Than Human by Theodore STurgeon Odd John by Olaf Stapledon
Post Apocalyptic: The Day of The Triffids by John Whyndham Earth Abides by George R. Stewart A Canticle for Lebowitz by...don't remember
Space Opera/Adventure: any of The Culture novels by Iain M. Banks The Reality Dysfunction series by ...don't remember Hyperion series by Dan Simmons To Your Scattered Bodies Go by Philip Jose Farmer
Dystopian: We by Yevgeny Zamyatin <---highly overlooked, predates 1984 and Brave New World
But the Absolute Best would be anything by: Stanislaw Lem (Cyberiad, Futurological Congress, Solaris) Alfred Bester (The STars my Destination, The Demolished Man) or Samuel R. Delany (Babel-17, Dhalgren, Trtion, Nova) oh and Roger Zelazny's Lord of Light and This Immortal are both great.
Some of Philip K. Dick's stuff is great, but everyone recommends him. :)
almost forgot John Brunner, check out Steel Beach, The Sheep Look Up, and Stand on Zanzibar.