SOLVED. General fiction. A boy is supremely gifted at making maps and diagrams, like his mom. The book is full of illustrations of the maps and diagrams. He hops a train to go join some secret society. Spoiler. [s]

[Marc *Dark Reader with a Thousand Young! Iä!*]

(I may not have the details right; the thing about him being a genuis scientific illustrator or whatever and the actual illustrations in the book should make it easy to identify by anyone who's read it and remembers the title.) He lives on a farm with his mom and dad; dad is serious, mom is creative. He runs away from home, tricks a train into stopping by faking a red train traffic light. SPOILERS it turns out that his mom was in on the whole thing and made the opportunity for the boy to pursue this goal, of joining something or obtaining an award that he thought he wasn't eligible for because he was a minor.

Read in 2000s, maybe early 2010s. I think it had a red cover.

[Joseph]

This looks like The Selected Works of T.S. Spivet, by Reif Larsen.

[Marc *Dark Reader with a Thousand Young! Iä!*]

That is it! And it’s already in my profile, sigh. It’s a book that I’ve forgotten more than once.