I had never seen this, but I'm glad now that I have. The basic premise of the story is a dramatic biography of Henry the VIII. There is some fictional license taken with history, but for the most part it stays faithful to the real thing. You can see why Henry did some of the things he did. By and large, the best thing of the show is that it portrays all of the characters as complex and three dimensional. A few are cartoons, like Bolin Sr. and Henry's one and only real challenger to the throne, but there are reasons for that. Specifically both are mechanisms for advancing the plot and showing in part why Henry is able to get away with some of the things he does later.
Ann Bolin is easily the most interesting and complicated character in the story. She starts out the sister of one of the ladies and waiting and the daughter of the ambassador of France and goes from there. She plays Henry like a fiddle, and does so in a way that has disastrous and yet fortuitous consequences for England and to a lesser degree all of Europe.
That's the thing I like the most about the show; its ability to integrate these complex characters and historical forces and make them come to life before our eyes rather than sit as well written passages in dusty historical tomes. With the Tudors we see the emotions and motivations of the characters, how they conflict and thus what causes them to act the way they do, especially understanding the larger and more important historical conflicts that take place after Henry's death.
I recommend it.