I thought the Dune series was most excellent. Also any Asimov books. I also quite enjoyed Hal Clement's Mission of Gravity. As for lighthearted...you can't g

I thought the Dune series was most excellent. Also any Asimov books. I also quite enjoyed Hal Clement's Mission of Gravity. As for lighthearted...you can't go wrong with The Hitchhiker's Guide to the Galaxy.