Awesome mind-bending, thought-provoking book in a narrative form, but that covers philosophical issues. By the creator of Dilbert! He must have been thinking about some interesting things during those cubicle days. :)
I thought this book was really nifty when I first read it. Then I took a philosophy class and realized all Adams did was throw a bunch of well-discussed philosophy questions together and stamp his name on it. There's a speck of originality.