Note that there is a book called "AdvancED Flex Application Development: Building Rich Media X" http://www.friendsofed.com/book.html?isbn=1590598962
I skimmed through at the bookstore, reading a few pages here and there. In my opinion, it didn't deliver on the promise of the title. It didn't offer much more than what can be learned by using free on-line resources. I ended up buying Flex Cookbook 3 (+1 from me as well). Another book I would recommend for advanced user is "Flex: training from the source". They talk you through from start to finish on how to build a complex on-line store application. I read the Flex 2 version about 8 months ago. It has now been updated to a Flex 3 version (http://www.amazon.com/Adobe-Flex-3-Training-Source/dp/0321529189).
