Originally Posted by Iucounu
G�del, Escher, Bach: an Eternal Golden Braid (not exactly sci-fi but includes fiction and essays on science), by Douglas R. Hofstadter
The Mind's I (more thought-provoking essays that include sci-fi), edited by Hofstadter et al.

I cannot recommend GEB too highly.

Also, most things by Bach.

http://www.amazon.com/Jonathan-Livingston-Seagull-Richard-Bach/dp/0380012863