As mentioned by previous reviewers, this book is excellent, well structured, easy to follow and leads you by the hand and gently releases you as the book progresses. A lot of thought has gone into how to explain things and highlighting potential pitfalls. It really does take you through by telling you, in written english first what you are going to do eg create a private method called xyz which returns void and accepts these params. It then shows you the correct code so you learn as you go, it then explains what this code is for/does and more importantly, why it is needed.
There is quite a bit of 'write this section of code' which is then re-written later in a more re-usable manner but this is actually a great way to learn how the application is being built and then learning how to do it efficiently.
An experienced programmer may find it a bit too basic in the early stages but stick with it, it does take you right through the building of an online grocery store.
Only -ve is the latter chapters tend to be a bit thinner on explanation, however, there is no detracting from the amount you will learn from this book and more importantly, your understanding of how to really use Flex.