I didn't get much of a chance to do a deep dive into Dynamics AX 2012 Development Cookbook http://www.packtpub.com/microsoft-dynamics-ax-2012-development-cookbook/book
In my opinion the book comes handy for a developer to directly jump to the topic which they are interested in rather than scanning chapter by chapter.
However I think some more areas the book could have covered is:
a. Enterprise Portal
b. AX Administration (Models administration etc)
d. Reporting and Analytics
Maybe I'm asking bit more from a development cookbook, Just my 2 cents - with AX 2012, there's a lot of integration happening with other Microsoft technology stack like VS.Net, SQL, SSRS, SSAS, etc so maybe the future versions of the book should cover more on these areas as well.
However, I would recommend this book for a developer as it's quite useful when it comes to day-to-day development tasks. Again Good work by the author and keep it up!