I found the book immensely helpful to kick-start a Pylons project I am working on. Every question I had in mind about how something worked was fully answered in the corresponding chapter. If you worked with Rails or Django and interested in Pylons, definitely get this book.
Its not all rosy, however. There are two things about this book that don't let me give it a 5 star rating.
First, there is an inconsistent assumption the author makes about reader's prior knowledge of web development and MVC frameworks. Some chapters would be harder for me to understand without my previous experience with Ruby on Rails, so I wonder if people without similar backgrounds could follow through. Yet some other chapters are obviously written for people without any web development experience: they are overly verbose and waste time needlessly explaining basics of web, http, caching and so on.
Second, the book isn't very smooth in its transitions from chapter to chapter, like if it was written by different people. I suspect this isn't authors fault but simply a reflection of what Pylons is. Since different parts of Pylons (views, form handling, ORM, routing, etc) come from different people they aren't always smoothly integrated and this fact gets reflected in the book as well. But hey, that's the whole point of using this framework!