This is a detailed document describing HTTP/2 (RFC 7540), the background, concepts, protocol and something about existing implementations and what the future might hold.
The contents are translated into several different languages.
See https://daniel.haxx.se/http2/ for the canonical home for this project.
See https://github.com/bagder/http2-explained for the source code of all book contents.
The document is distributed under the Creative Commons Attribution 4.0 license: https://creativecommons.org/licenses/by/4.0/
I encourage and welcome help and contributions from anyone who may have improvements to offer. We accept pull requests, but you can also just file issues or send email to firstname.lastname@example.org with your suggestions!
/ Daniel Stenberg