What is YA, anyway?

I’ve been thinking a lot recently about what makes a book YA. I write both YA and adult: in June, I was editing a YA book; now, I’m editing an adult book. I also read both YA and adult, but although I’ve stopped tracking my reading in any great detail and therefore don’t have stats to hand, I would suspect that I’ve been leaning more towards adult books in recent months.

This makes sense: I’m 25. I’m an adult. I’m worried about things like finding a job and being able to afford rent and the f...