Maximum chapter size?

[ddevans]

I'd like to publish an entire book (54k words) as a single volume. When I attempt to save a draft it fails out with the message "You cannot edit this." Is this intended or a bug? If it's intended, what is the maximum chapter length so I can cut it up as little as possible?

 

[ddevans]

Follow up: It's at least 38k. That's a natural split there I can live with.