The pile of development books on Microsoft Dynamics AX keeps growing. Here is an overview (ordered by publication date):
Microsoft Dynamics AX 2009 Development Cookbook - 2009 - Dynamics AX 2009
Solve real-world Dynamics AX development problems with over 60 simple but incredibly effective recipes.
Microsoft Dynamics AX 2009 Programming: Getting Started - 2009 - Dynamics AX 2009
Get to grips with Dynamics AX 2009 development quickly to build reliable and robust business applications.
Inside Dynamics AX 2009 - 2009 - Dynamics AX 2009
Dig into the architecture and internals of Microsoft Dynamics AX—with firsthand insights from the team who designed and developed it. Deepen your knowledge of the underlying frameworks, components, and tools—and get best-practice guidance to customize and extend your own high-performance solutions.
Inside Dynamics AX 4 - 2006 - Dynamics AX 4.0
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.
Dynamics AX - A guide to Microsoft Axapta - 2006 - Dynamics AX 3.0
This authoritative and comprehensive guide walks you gently through the bulk of what you need to know to productively apply the system in the real world; with real data, sizing guidelines, deployment architectures, and code.
MorphX IT - 2006 - Dynamics AX 3.0 SP4
MORPHX IT's target group is newbies to AX development. If you want to save time on learning AX development, wants to catch up on a certain area or if you are working as a Dynamics AX functional consultant and want to learn some about AX development, then MORPHX IT will beneficial for you.
If I missed any - please do not hesitate to let me know.