Had I written this review after about a month with this book, I would've given it very high marks. However, after several months with it, attempting to us it in a real Rails 3 project, I find it wanting.
It's billed as a reference for Rails 3, and seems intended as something to have dog-eared, by your side, while cranking out a Rails app. In my experience over the last several months, it has been a source of frustration, providing me with little more than introductory information on topics that, sadly, are better covered by the rails guides or in various blog posts.
The section on Active Record, specifically on querying, is very light. It's mostly a printout/summary of some of the methods available, with no substantive examples, or anything close to what might be required in the real world. AREL is barely mentioned; all we get is a link to the github page.
There are two bigger disappointments: testing and AJAX.
Testing: Testing is not even listed in the index. Let me repeat that: Testing is not even listed in the index. There is a chapter on RSpec, which is wholly out of place, most of the chapter just dealing with general RSPec stuff. There is some rails-specific stuff, but overall this is IT for testing. Again, the tools and APIs Rails provides for testing are powerful, but very weakly documented, and this book completely drops the ball on filling in this crucial gap. I find it rich, since the Rails community prides itself on testing. Additionally, it seems inconsistent with other non-Rails-default choices (Test::Unit being the default); HAML is used in all view examples, yet there isn't even a mention of it as being nonstandard, nor is there so much as a SIDEBAR to explain how it works. While I personally think using HAML was a bad choice, if the case is to be made that it's superior; at least throw people a bone so they understand what it is, why it should be used, and how it works.
A big chunk of the book is simply formatted API documentation. This information can be easily found online, and is far easier to search.
Given all of this, I've found that The Rails 3 Way has not ONCE provided me with the answer to an issue I was having building what I believe to be a very simple website. Every time, I've closed the book and searched the web, often finding clear and cogent explanations; the exact things that should be in this book!
A book that touts itself as a reference for advanced Rails development should provide more in-depth explanation of not just how things work, but how to go about discovering advanced features and diagnosing problems.
If you are looking for introductory material, I'd advise against this, and if you are looking for more advanced coverage, again, I cannot recommend this book.