The product page for AWDWR4 includes two paragraphs, including this one:
Rails 4 introduces a number of user-facing changes, and the ebook has been updated to match all the latest changes and new best practices in Rails. This includes full support for Ruby 2.0, controller concerns, Russian Doll caching, strong parameters, Turbolinks, new test and bin directory layouts, and much more.
Shockingly, the first printing of AWDWR4 includes no discussion of some of the aforementioned changes, including Turbolinks and strong parameters, which are the first two subjects I searched for in my PDF copy of AWDWR4. The authors simply included a link to Turbolinks’ GitHub repo, and there is literally not one mention of the term “strong parameters” in the whole book! AWDWR4 seems to be a hastily-updated version of AWDWR3, which I also own.
If you already know Rails 3, I recommend that you not waste your time or money on AWDWR4. After realizing that AWDWR4 is worthless, I bought a PDF copies of Rails 4 in Action and The Rails 4 Way. These two books are currently in beta, but they’re already over 700 pages long and they include sections devoted to strong parameters, Turbolinks, etc.
In the past, I bought Pragmatic books without bothering to evaluate them beforehand because their books had always been high-quality. This seems to no longer be the case, and I won’t buy another Pragmatic book until one is recommended to me by someone I trust. Pragmatic joins O’Reilly in this regard.