There are two kind of development books worth reading, first breed concentrates on quickly becoming proficient on the most needed tools without going into details, the second type is more aimed to developers who already learned the basics and need learning intermediate to advanced proficiency of the technology. Though Express web application development contains grains of the former it is fine example of the latter.
At the time of writing this review I've been using Express for more then a year and I'm duly impressed with the quality of the framework and the feel of production ready, everything you really need approach. The creator of Express TJ Holowaychuk has become my first option for high quality node.js libraries, express,jade,stylus,mocha,mongoose to name a few.
The author of this book fallows a fine tradition of presenting real life needs using code that just works and builds on top of it with explanations of the express functionality .
All the area covered routes, response, jade, stylus etc improved on my understanding of express and this book has become my reference material in my development.
My only nitpick is crave for more material, in order for this book to become "bible" of end to end web application development it needs to add two chapters that cover the database layer with mongoose and testing your application with mocha.
In conclusion I recommend this book for both those new with express and especially those who already wet their feet with express and need book that could teach real life usage and serve as a reference book for express.