if you don't want to know the story of Mirrormask before you see the film, don't buy this book.
if however you do want
a)to experience a tittilating insight into the creative proccesses that went into developing it
b)to see the story in the fractured dimension of itself that it was, is and never will be
c)to appreciate concept work that is far more than your average storyboard
d)to read and see a good tale irrelevant to the fact that it is also a film
e)all of the above,
then you might as well, it is a very pleasing weight.
if you have seen the film or never heard of it then the above is as relevant as you think it is.
This is just one of several books being brought out around the film Mirrormask, think of them as extras on the second DVD that, because neither creator has ever been afraid of working in different mediums have been brought out in book form, before the theatre release of the film. And a book is a far nicer thing to own than a disk that you won't get round to watching for ages and will probably get scratched anyway.