Well, it is the ONLY book on Twisted, which I love (as I like Event-driven programming), but it still fails to be more than a cursory overview of Twisted, and it even partly fails at that, as every chapter seems to be independent and just describe the protocol at hand, instead of the framework as a whole.

To its defense, it is written in an easy going style. To read it, you need to understand both TCP/IP (and its applications) as well as Python, or you will be totally lost.