The Book Marketing Society in association with The Guardian has launched a nationwide (UK) promotion to find the book that best defines the 20th century. The promotion features a review of 50 specially selected titles and editorial features on the "groundbreaking" books defining the various decades of the 20th Century.
Full list of titles.
You're welcome to vote.
Books that define their era, not describe it. (I admit I'm still stumbling over whether it defines or describes the 80s, but I think American Psycho should be on the list. I think.)
Guardian books blog discussion (in which it is noted that Patrick Hamilton's era-defining The Slaves of Solitude was overlooked).