I just found out about The Shackled City recently from some folks over on the Monte Cook's Iron Heroes messageboard. I got both the Shackled City and the Dragon Compendium and I'm very impressed with both.
If Age of Worms is as good or better than the Shackled City, I will buy it if and when it's made into a hardback package like the Shackled City. I really hope there are plans for this to happen!