Master the Markets is a very watered-down version of Williams' first book, Undeclared Secrets. MTM is largely written to sell an expensive, unecessary piece of software, with info of value from the first book removed in large quantities.
The DVD's are good, and do cover some things not clearly or extensively explained in the MTM book, as well as being closer to the focus of the first book. TradeGuider charges an absurd price for them (along with everything else they sell), but the presentations are a good starting point.
They used to do a free Chart of the Week presentation that was often quite good as well, but now they figure they've got enough fished hooked by screaming about market manipulation and an obvious call in the oil market, so no longer do these.