XML is one of those technologies you take for granted as a Flash developer and probably use practically every single day without giving it a second thought. That said I was interested to see if "Foundation XML for Flash" would be my cup of tea and go beyond the typical introduction to the XML object in Flash.
I must say I was pleasantly surprised, the book offers a whole lot of information you seldom see covered in books on XML and Flash including XSLT, DTD's, namespaces etc. One of the major strengths of this publication is the chapters where Flash integration with XML files taken from Word, Excel and Access are discussed. Its something I hadn't really thought of before and opens up a whole new world of possibilities for Flash applications interfacing with documents, spreadsheets and databases and definitely an approach I'd like to try with my install of OpenOffice.
One thing I didn't see covered was the idMap property of the XML Object that was introduced for Flash Player 8 but other than that, this book is a must-have reference guide to Flash and XML, highly recommended!
If you want to get started with Flex there is no better way than sitting yourself down and start experimenting with this book next to you on the desk. Although there's not much choice of books on Flex, this one I've found is exceptionally well-written and will guide you through all aspects of RIA development with Flex. Something to take into consideration is that "Developing Rich Clients for Macromedia Flex" is not a book for absolute beginners - you ideally need to have some background knowledge on ActionScript 2.0 and OOP methodologies before you get started.
The guys from iteration::two (soon to be Macromedia Consulting EMEA) did an excellent job on this book, hope they'll do an update for the next release of Flex.