I normally try not to take too much from science fiction. Mostly because
science fact offers such a wealth of questions and activities, that it is more than enough to keep me busy.
Still, I love reading SciFi when I have free time.
The Guardian
http://www.guardian.co.uk has been kind enough to post a list of its favorite 1,000 SciFi and Fantasy books. You can get the Guardian's list at
http://www.guardian.co.uk/books/2009/jan/22/1000-novels-science-fiction-fantasy-part-oneOne of my personal favorites on the list is Arthur C Clarke: Childhood's End (1953).
Cheers!
-stu