As someone who has relatively little experience with Flex, I found this book to be a great asset in furthering my understanding of how and why things work the way they do not only in MXML, but also on the ActionScript side.
The tone of the book is very friendly. As a general rule, I did not find myself bogged down in technical terminology. A good balance was struck between keeping things simple for the average reader, yet still technical enough to hold the attention of somebody with more in depth knowledge of previous versions of Flex.
The book also starts out with a nice section on the benefits of Flex and RIA’s in general along with a few pointers on how to sell upper management on its use. From there they move on to cover the basics of ActionScript and Flex and show how MXML layout works, how MXML and AS work with one another, some basics on how to work with data inside of your application and also detail the differences between the old Halo controls and the new Spark controls.
The second section of the book delves into more complex topics like the event model, view states, writing custom components and more. There is a small jump in the assumed capabilities of the reading audience at this point. Readers who are new to Flex and who have worked through the first part of the book should still be able to follow along at this point.
The only negative that struck me as I was reading the book was the code samples. While they do an excellent job of demonstrating the topic that they are associated with, I would have preferred if by the time I reached the end of the book I had a fully working reference application vs a series of smaller individual apps.
Overall, I enjoyed reading the book and learned quite a lot, not only about Flex 4, but Flex as a whole. The authors did a good job of keeping the subject matter entertaining and making their various contributions flow seamlessly together.
I would recommend this book both to people who are staring out in Flex development as well as people who are already familiar with Flex and looking to find out what is new in Flex 4.
You can pre-order your copy on Amazon