DDS began the story and DDS2 finishes it – with some unforseen twists in true MegaTen style along the way. DDS2 has all the ingredients of a true MegaTen, in fact, it's one of the best RPGs I've ever played, and along with DDS is numbered in my top 10 RPGs of all time.
The Press-Turn Combat of DDS has been polished in DDS2 so that it's smoother and a ‘Berserk’ (half demon-half human) form has been added that allows you to rack up some amazing hits. The Mantra Grid has also had an overhaul so it's in a ‘honeycomb’ shape rather than the stright lines of DDS. This means that your characters can learn anything, anywhere on the Grid.
Although your stats from DDS don't carry over to DDS2 the story tells you why – still, no consolation for those of us who maxed out our stats in the hope of starting the next game a little stronger. This means that DDS2 can be played as a stand-alone game (although why anyone would play it without playing the first is beyond my ken).
There's not alot of room here for me to ramble on about this amazing RPG so I'll just say Buy it! Play it! Become a true believer!