As a follow up to a comment on another post about the lack of intermediate/advanced books for web developers, I'd like to kick off a discussion of such books[1].
I'll start: High-Performance Browser Networking, an excellent intermediate-level books that delves into the specifics of various web protocols: HTTP, WebSocket, XMLHttpRequest, etc, and how to tweak them for performance [2].
1. https://news.ycombinator.com/item?id=9910440
2. http://chimera.labs.oreilly.com/books/1230000000545