This smartly designed softcover consists solely of the number pi, calculated to 5,000,000 decimal places. By far the biggest pi ever published in book form. It sprawls across 558 oversized pages, big as a city phonebook. Practical? Not really. Cool? Definitely. And if you really want to go whole hog, consider grabbing the primo edition: a beautiful, glossy hardcover [available here]. (For a smaller - but still pretty darn big - dose of pi, check out Pi to Two Million Places.)