I have actually read and seen both the book and the movie. I was so gripped with the whole plot and the artistic production and illustration of the book( & animation of the movie) that I literally glued my eyes to pages until I finished the book (& the film).
It’s about Helena, daughter of circus performers, who wants to escape her extraordinary life and live a normal one. Apparently, in another realm, a magical one, a princess who looks just like her wants to escape and live a normal life too. With the help of a mirror mask, the princess was able to steal Helena’s “not-so-ordinary” life while Helena was transported to the Princess’ magical Kingdom. A series of unique plots and twists reveal quirky and amazing characters. Neil Gaiman is indeed a genius. I wonder how he comes up with such out of this world concepts. Read it! I promise you, you're going to be amazed by it.