hooks at chapter endings
[And to be semi-on-topic ... I'm wondering if it's necessary for every chapter to end with a hook, or only the first few? And how strong does a hook have to be? Deadly peril, or teasing clue, or mild curiosity?]
My general thoughts on this are that every chapter should end with a hook of some sort, even (or perhaps especially) if it's "What on earth happens after that?". "Why did that happen?" or "Why did he say (or do, or think) that?" or "Who (or what) is this just come into the room?" are also good end-of-chapter questions. I think the kind of hook largely depends on the kind of story you're telling. A comedy of manners will obviously have less deadly peril than a thriller. Then again, perhaps social death counts.
I think the hook should work together with the pacing and the tone of the chapter--though that's not to say it couldn't be in contrast. Perhaps you expect deadly peril and it turns out to be a joke; but the deadly peril may come from another direction entirely, and we must read on to find out which it is. Well-done humour is a good place to look for hooks, because humour depends on creating and then inverting expectations, which a hook, in my opinion, does.
Douglas Adams is good for hooks, particularly in the later books. I can think of good examples from 'Life, the Universe, and Everything'--think of Arthur Dent and Ford Prefect jumping onto the couch and falling through a crack in space-time to the cricket ground. It could be a joke--it could be deathly peril--it could be all sorts of things, most of which it turns out to be, or lead to. And it furthers the plot (insofar as it exists), the character development (such as there is of that), and the theme (if you can figure it out).