[otrs] ITSM first steps: What is this ITIL, then?

Hi, We're going to look into the ITSM module for OTRS. But before that, I think I need to get a primer in the ITIL process. Can anybody recommend a good introductory book (preferably, I seem to learn best from paper for some reason)? Not the "bible" or "be all end all" of ITIL, just a sort of "ITIL for Dummies" kind of thing? Lars