Gives a very nice overview of ActivityStreams2.0, ActivityPub API for clients and AP protocol.

I read a pre-published version which had some small errors in code examples and I wasn't able to set up the ap python example client that's menitioned in the book on my GNU/Linux machine. For me personally the nodejs AP server examples were also hard to understand since I avoid javascript whenever I can.

Next steps for me are reading the code of projects I'll understand, referring to landrok/activitypub php library, the activitypub and activitystreams drupal modules, pixelfed etc. This activitypub development list also looks delightful: codeberg.org/fediverse/delightful-activitypub-development