Don't take too long to think about it. Fifteen books you've read that will always stick with you. First fifteen you can recall in no more than 15 minutes.
the iliad - homer
the odyssey - also homer
lysistrata - aristophanes
the hero with a thousand faces - joseph campbell
the hobbit - j to the double-r tolkienz
slaughterhouse-five - kurt vonnegut
catch-22 - joseph heller
the phantom tollbooth - norton juster
rules for radicals - saul alinsky
a people's history of the united states - howard zinn
moby dick - herman melville
the road - cormac mccarthy
house of leaves - mark z. danielewski
gilgamesh - nobody knows D:
atlas shrugged - ayn rand (THIS ONE IS NOT A POSITIVE ENDORSEMENT)