Oddly, it seems to be working today. Must have been a temporary thing.

Looks promising. Just FYI: on your Quick Racket Tutorial page (https://leanpub.com/racket-ai/read#leanpub-auto-a-quick-racket-tutorial), your link to Racket Essentials (https://docs.racket-lang.org/guide/) redirects to https://leanpub.com/racket-ai/The Racket Guide which gives an error: “Something is missing — I’m sorry, but the page you’re looking for is no longer here.”