1967 Bantam paperback edition of Thomas Pynchon's The Crying of Lot 49*
I love old paperback art, and this one is no exception. Paisley designs should be integrated into far more book covers.
Also, I highly recommend this book to anyone interested in a bizarre, off-the-wall, novel that still manages to retain a concrete hold on its plot and characters. (It's also short!) Pynchon's prose expresses the most everyday actions in strikingly unique ways, and for that I adore it.
* I hate it when items that normally appear in italics (i.e. book titles) appear inside other items that normally appear in italics (i.e. picture captions) so that the italics cancel each other out and the former must then be unitalicized. It just looks wrong to me.