This question is slightly less problematic than where do children come from, so you’re more likely to encounter it in polite conversation. Or, if you’re me, you get it in statement form, shortly after someone discovers what I do. Like so (imagine it with swanky Ed Briant illustration):
AK: You’re a derivatives trader? That’s cool. I’m a children’s book editor.
Mr. Derivatives Trader: Children’s book editor? Huh. Say, I’ve got some story ideas I’ve been thinking about having illustrated . . .
So you see, children’s books come from high-powered executive types (or entertainment professionals) with time to spare.
Actually, before my most recent encounter with a subspecies of this exchange, I heard this excellent story on NPR, about author Deborah Wiles, who spends a lot of time doing school visits and talking to kids about where stories come from.
I suspect kids have always been interested in process and smart authors have done what Ms. Wiles is doing for years, but there is an added layer to this interest in process and origins that feels fairly new to me—that is, awareness of release dates. When I was reading in elementary school and junior high, I don’t feel like I thought of books as new or old. Books just existed. It never occurred to me to wonder when The Tripods books came out or when there would be more of them. Yet, as early as junior high, I was acutely aware of the release dates of albums, probably through MTV (I remember walking to the mall to get Pearl Jam's Vs. the day it came out). Now, of course, kids are often acutely aware of release dates—and not just of blockbusters. I’d venture to chalk this up to Harry Potter, but I’d love to hear earlier tales of release date anticipation, if any exist.
(Speaking of anticipation, wouldn’t it be cool if we could do publicity stunts with readers like this one that Paramount did in advance of the new Star Trek movie?)