David Friedman is considering a third edition of his classic The Machinery of Freedom, and he's soliciting input regarding what to include and what to exclude. If you're familiar with the book and have an opinion, now's the time to express it!
This was the book that convinced me that I was a libertarian (and, for that matter, explained to me what a libertarian was). It's also the book that explained what kind of libertarian I was not. I think every libertarian should read the sections at the end on why most simple libertarian arguments about force don't make sense.