How do books work?

I woke up this morning before the sun wondering how to get from point a to point b, and trying to remember how others do it. The point a I'm thinking about is sometimes called "part 1" and point b is "part 2," or in series of novels telling one story, volumes one and two.  Having decided that I wanted each part to feature first person narration, but with two different narrators. I read somewhere the first person narration was forbidden in fantasy fiction, but also that it was normative in young adult fiction. But putting aside genre for now (and perhaps forever), the rationale for a first person narration in a novel with young adult protagonists is to convey their perspective (and only their perspective). My thought was that the narrator of the first part would be a secondary but important character in the second part. The third part would be in the third person, so that I could have both main characters (and others). Do I know of any other works that employ this structure? Not off hand, but I'll take that to be a good thing, not a bad thing.

In the movies, there must be a great car chase, a bad guy must get what's coming to him (or maybe her or it), the protagonist must survive (though there could be doubt about this), but the job cannot be done. Jason Bourne survived the first movie, got the girl, killed the bad guy, and then went off to live in anonymity and obscurity in Goa. But for some inexplicable reason, other bad guys saw the need to come all the way out there and kill his girl friend, so now there's a motivation for the next installment ... At the end of every Harry Potter volume, the kids win the game (while nearly perishing), and go home for the summer, to do it all again next year. The pattern is a little more troubled toward the end of the series. In LOTR, there is only one continuous story, broken every five hundred pages, or three hours, at a convenient turn in the story. But nothing with respect to the main quests (those of Frodo and Aragorn) is resolved at the end of volumes one or two: that can't happen until the end of the last volume. Similarly, in His Dark Materials, the endings of volumes one and two are provisional, and not very hopeful. In many ways, things keep getting worse and worse. New characters are introduced along the way and carry the story forward, while sometimes the previous main characters disappear (always to re-appear): Lyra and Will must be there at the end, just as Frodo and Aragorn must be there at the end. Maybe JKR could have actually killed off Harry (or one of this chums) at the end, but we all knew that he would prevail against Voldemort. The ending of Harry Potter is somewhat unsatisfying because here are all these main characters, all grown up and ready to do an adult's work in the world, and there's nothing left to do. We see them middle-aged, living in the suburbs, sending their kids off to a safer Hogwarts. LOTR has the right side winning at the end, but in true epic saga fashion, the main characters pay a price for their ordeals. Aragorn faces mortality and Frodo goes into "exile," sailing into the West. Pullman has the darkest and most provocative vision -- no wonder so many hate him: in the end, the kids have sex, God dies, and Authority falls from the sky. It's the ultimate "adolescent" happy ending.

My hesitation has nothing to do with not knowing how books work. I've read enough good ones and bad ones to know what works and what doesn't, and to know that anything can be made to work with the right combination of imagination and skill. Also, it is clear that good writing is motivated by deep and long thinking about everything, which then finds its way into a story. In this sense, all these stories are parables or fables. I'm sure what I eventually come up with will be no less a reflection of what matters to me -- even if I'm not sure what that is -- and what I know and what kinds of tricks I can perform. Sit up, shake hands, roll over.