The PF APs remind me of Call of Cthulhu adventures in that they tell a story, print some stats, offer a couple of tips for how to GM certain portions, but it is really up to the GM to translate it into a session of gameplay. I am currently preparing for a CoC one-shot (The Dead Light by Alan Bligh) and I have been making a kind of flow chart out of the module text. You certainly cannot crack open one of these for the first time an hour or two before the session, unless you don't think your players will get far at all.