More of Divinity 2's great gameplay with better graphics.
Dragon Knight Saga, to begin with is excellent value for your money. I played Ego Draconis and liked it a lot. When I'd bought it, it was due the sole reason that far as I knew it was the only half decent game where you could play as a dragon. The game didn't disappoint. There weren't any surprises, gameplay-wise. It was good solid hack and slash, RPG fun (kind of like Morrowind) and a decent, albeit cliched story.
The Dragon Knight saga, to put it simply, builds upon the first game. While the new addon itself is an entire game to be enjoyed, Ego Draconis too has been overhauled with major changes made. The game now has some of that polish that the predecessor so sorely lacked. For one, the graphics are better looking. And thankfully the bugs are gone.
Now, the story Ego Draconis, while it was in no way stellar, but it had a very unexpected ending. Many fans were rather put off by it (myself included). Flames of Vengence, the addon in this pack, continues that story. As for gameplay, it's still the solid old Ego Draconis gameplay.
So all said, the final word is that if you liked Ego Draconis, you want to get this. If you did not like Ego Draconis, then you still want to try this out, because this time around everything a lot more snappy and polished. Maybe you will like it this time around and will rave about as the best game of the year!