Apparently there's a book that came before the movie, published in '68 by 2 people going under the pen name Richard Hooker, and then came a sequel after the success of the movie. MASH: A Novel About Three Army Doctors followed by MAS*H Goes To Maine.

I didn't known this before having to look up Frank's name. And I'm not sure, thankfully, that my dad knows this or he'd definitely be on the lookout for copies any time he's at a thrift store.