Funny you should mention it, that's (part of) the topic of my latest, about designing nonfiction like a problem-solving product (won't plug it here since it's off-topic, but easy enough to find).

Too many authors seem to forget that readers pay for every book twice: once with the cover price and then again with their time.

(And for most business/tech books, the second price is orders of magnitude more costly than the first.)

Anyway, happy it has proven useful and many thanks for the support.