I don't think I could ever recommend just one book . . . I've thought about it since this thread started and simply can't accept the premise -- even though the exercise is useful. I agree that Hofstadter's _Goedel, Escher, Bach_ comes close to meeting this standard, though. I DO have "most recommended" books, though. Over time GEB is on this short list, as is Persig's _Zen and the Art of Motorcycle Maintenance_ and Howard Buss' _The Evolution of Desire_. Recently, I've been pushing Steven Pinker's _How the Mind Works_ pretty strongly.
BTW, I keep an annotated bibliography of every book I read (how obsessive!) on the web at:
Greg Burch's Reading
Greg Burch <GBurch1@aol.com>----<email@example.com> Attorney ::: Director, Extropy Institute ::: Wilderness Guide http://users.aol.com/gburch1 -or- http://members.aol.com/gburch1 "Good ideas are not adopted automatically. They must be driven into practice with courageous impatience."
-- Admiral Hyman Rickover