"This is a book of tables for the "context" phase of creating an adventure; it contains table for generating fantastic locations, missions, patrons, villainous plans, and unusual minions. "I really like it. I've only played about with it a little bit, but already I can see its great potential for making my life easier.
My experience largely mirrors that of James Smith over at The Underdark Gazette, so rather than repeat him pretty much verbatim, I'd suggest you go and see what he has to say about it. (He also has lots of other good stuff over there; if you haven't encountered his blog yet I recommend that you give him a read).
MADD (Volume 1) is basically a collection of interconnected random generation tables designed to give the overburdened DM's imagination a shunt, rather than to churn out a complete adventure with every T crossed and every i dotted, and it succeeds in that aim admirably. Not having seen any of the other volumes, I don't know how well they succeed in continuing the process, but on the basis of this first one I'm optimistic.