I am new to Flex programming. I am an experienced J2EE developer and have done a fair bit of RIA programming using non-Adobe technologies..
Can you please suggest one or two good books which cover Flex 4 and AS3 programming in depth.
PS: I am not looking for beginner level books, I need an intermediate to advanced Flex programming bible.
Adobe Flex 3: Training from the Source. I was in the same place as you and this let me pick up the key stuff extremely quickly. Though this might be a bit outdated for Flex 4, but as far as I have scratched Flex 4, looks like the basic concepts you learn from this book are still highly applicable.
When I started with Flex I picked "Adobe Flex 3: Training from the Source" and "Flex 3 Cookbook" from O'Reilly. They helped me a bit with the basics but the most used source was the good original Flex documentation.
If you are looking for really advanced information, the internet is the number one source! There are very good articles and tutorial on the Flex Developer Center. Also always a good source is http://blog.flexexamples.com/ and there are many more ...
It's not a book, but the AIR application "Tour de Flex" is an example-based (~200) tour of the various Flex components, complete with source code: http://www.adobe.com/devnet/flex/tourdeflex/. I wish it was around when I got started.
The authors of Adobe Flex 3: Training from the Source have put out a version for Flex 4, and in a few months the more advanced volume 2 will be released. The authors of this series are very good and often on Twitter.
Another book that I liked a lot was the Flex 3 Bible. A new book was released for version 4 -- Flash Builder 4 and Flex 4 Bible. This is a massive book that covers beginning through advanced.