Seeing that a lot of what has been suggested is books by male authors (that's ok, that is, really), I'd like to throw in a couple of books written by women in the mix. Once again, I'd like to clarify that these are books I like and happen to be written by women, before I start some kind of wildfire.
Zadie Smith - White Teeth
Doris Lessing - The Golden Notebook
There are more books I'd love to discuss, but these two are probably what I want to discuss most.