Guys, stay away you will be bored. Gals, you will like it my wife and our 17 year old daughter liked and thought it was fairly true to the book, which I have no plans of ever reading. So see it if you like the books and a female, most males should stay away.
If you have not seen a Miyazaki movie, or only like computer animation you need to see this. Miyazaki's color palette fills the screen with all the great characters and creatures he creates. The underwater creatures are amazing! This story is a different take on the little mermaid fable. Children will love it and adults will wish they were children again, if only to life in the realm of Miyazaki. You also get little touch of environmentalism, which is always part of Miyazaki's love for the earth. If you don't want to go to theater, I would recommend Howl's Moving Castle, Princess Monoke, Castle in the Sky, and/or Spirited Away, until this dvd comes out. These will prepare you for the greatness that is Miyazaki.