Frank Herbet's Dune, a must read.
Dan Simmons' Hyperion:
http://inkmesh.com/ebooks/hyperion-d...k/?qs=hyperion
Orson Scott Card's "Enders Game". (just plan an empty day, because I read it straight from cover to cover)
http://inkmesh.com/ebooks/enders-gam...ender%27s+game
Vernor Vinge's A deepness in the sky:
http://inkmesh.com/ebooks/deepness-i...ess+in+the+Sky