First off, before I review this, I have to say, Princess Tutu is my FAVORITE anime. Ever. And I've seen a lot. It's fantastic, and I think everyone should see it.
I'm not sure how to summarize the story. It's very complex and engaging. I have to mention first, this anime is very much like a fairy tale. (in fact it uses a lot of Germanic legend and folklore as inspiration) It focuses on a girl, who is really a duck, named Duck, who is in love with a Prince without a heart. She is given a pendant by a man named Drosselmeyer, who is the man pulling the strings behind the whole story. The pendant allows her to take the form of a human girl. This pendant also allows her to turn into Princess Tutu. While Duck is Princess Tutu, she can search for and retrieve shards of the Prince's heart. Throughout the series, Duck must face different obstacles, such a Knight whose role in the story is ambiguous at first, (is he friend or foe?) another Princess who claims the Prince is hers, and various people under the influence of the heart shards of the Prince. I won't say more than that, because I'm afraid I'll spoil this amazing story.
Keep in mind, Princess Tutu does have quite a bit of dancing, many episodes draw inspiration from famous ballets, and music from those ballets is used throughout the series. However, the dancing is beautiful, and even if you aren't familiar with ballet, the extras are there to help you.
This is the first boxset that ADV has done right. (at least from the dvds I've bought from them) They haven't stripped the extras, and there are a lot of them. Some of the extras include "Ballet for Beginners," (which explains the different ballet that are mentioned/used in the series) commentary from the voice actors and staff, outtakes, and tv promos, among other things.
I really can't say enough good things about this anime. At first glance, it may seem childish, but if you stick with it, there are a lot of mature themes going on throughout the anime. It has so many levels to it...it's simply amazing, that's all I can say. I'd recommend this for 13+ for some violence blood, and chaste nudity. (as in all you really see is the silhouette)