Inside Dynamics AX 2009 is available now and can be bought from Amazon. The book can be found here.
From the site
Take an inside look at Microsoft Dynamics AX 2009 and exploit that in-depth, architectural perspective to more effectively customize and extend your enterprise solutions. The authors members of the Microsoft product team create a real-world context for essential concepts, and expertly illustrate how modules interrelate and interact. They offer practical, scenario-based guidance and troubleshooting advice on topics ranging from business intelligence and workflow to integration, reporting, and performance tuning. The book also provides extensive cross-references to additional reference and system documentation. "