One I haven't seen yet..... (Score 1)

I'd agree with most of the other replies, there's one that I loved as a teenager that I haven't seen listed yet. The first book in the trilogy was 'The White Mountains' by John Christopher, the other two in the series are 'The City of Lead and Gold' and 'The Pool of Fire'. I first read this series when I was in elementary school - and loved it. The main character is young, although he's almost old enough to be capped (when you read it you'll understand).

As far as the other suggestions - Piers Anthony is great (definately review bio of a space tyrant before you read it together), Asimov, Heinlein, and Dune by Frank Herbert.