This book seems to be shipping now.
Here is an excerpt from the book description:
Dive deep in to the architectural details of Microsoft Dynamics AX to make relationships clear and development tasks easier. The first part of the book is aimed at consultants and developers who are new to Microsoft Dynamics AX but have backgrounds in business application development using traditional languages, frameworks, and tools. It describes the architecture and development environment and explains key application frameworks that developers need for their customization, extension, and integration projects. The second part of the book is a reference guide for developers who work with Microsoft Dynamics AX deployments, with information on developing new functionality and supporting users. It covers more complex development concepts such as advanced forms and reports, reflection over the application metadata, performance, upgrades, migration, and setup. This is the first book written by the Microsoft product group architects and the first to take developers deep inside Microsoft Dynamics AX.
Read more about the book here: http://www.microsoft.com/MSPress/books/9225.aspx
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