I personally don’t agree with what the other person commented but if you’d like to get a better understanding of the story, read the book. There was a lot of information that they didn’t portray in the movie, like the fact that Sophie is a witch.
Howl's Moving Castle https://www.amazon.com/dp/0061478784/ref=cm_sw_r_cp_api_i_pmmhFbP4555KP
The movie is based on Diana Wynne Jones novel, so yes!:D The book is pretty different though. For example there is no war in it.I have read somewhere that Miyazaki and her met and that she approved Miyazakis idea for the movie :D
That was actually my favourite book as a young 'un, Diana Wynne Jones is incredibly good. Would destroy JK Rowling in a beat down. I nearly fell off my shit when I heard Ghibli were making a movie of it...
Howl's Moving Castle, by Diana Wynne Jones. :)
edit: This is the one!
Howl's Moving Castle is based on a book! http://www.amazon.com/Howls-Moving-Castle-Diana-Wynne/dp/0061478784
Howl's Moving Castle by Diana Wynne Jones?
Maybe something by Piers Anthony?