Calvin and Hobbes is hands down, flat out, absolutely without-a-doubt the best comic strip ever written.
I have all of the books, including the Treasureys and Art Gallery Catalog.
If I had the money, I'd run to the store faster than Spaceman Spiff's hyperdrive. Alas, I don't, especially since I already have all the books.
I just started reading them again. About once a year I get in the mood and read all the books in order. My favourite story is the one in "The Days Are Just Packed" wher e Calvin and Hobbes go two hours into the future to get Calvin's homework, which the past and future Hobbes end up writing about the 3 Calvin's fighting.
Reading these books as I was growing up is almost the sole reason for my over-developed vocabulary.
I'd also like to get The Complete Far Side.