Of course, there is a lot of nuance in the OAuth spec(s), but we didn't feel the need to be that verbose for an "An Introduction to APIs". We'd love to hear more about what broad but important aspect of OAuth that we missed! We'll absolutely make revisions and updates.

Completely agree - that's the first time I've read a guide to oauth and actually understood it. So big thanks from me.

For OAuth, I highly recommend the OAuth Bible: http://oauthbible.com