You should! You have to read the book and then watch the movie, because I'm pretty sure everyone I've talked to found the movie really boring if they hadn't read the book beforehand.

That said, READ IT. It truly is the best book I've ever read and I'm totally not even using hyperbole there. The movie is kind of meh, but it's good because Alan Arkin is a perfect Yossarian and you get to see his butt because Yossarian is a horny bastard who spends a lot of the movie naked. Win! \o/