The engineering problem hiding inside "AI writes a book"

When people hear "an app that writes books with AI," they picture one giant prompt and a wall of purple prose. That's the demo version. The moment you try to ship a real reading-and-writing product, you find out the generation step is the easy part. The hard part is everything wrapped around it — and it's a genuinely interesting systems problem. A book is a state machine, not a prompt The first thing that breaks the naive approach is length. Ask a model for "a novel" and you get a vibe: a…