A friend of mine bought me Howl's Moving Castle for the recent holidays and probably like most others who also know there's a movie with the same title, knew the story by the anime counterpart.
I couldn't help it as I read, comparing the movie and the book. Sometimes that's half the fun, figuring out what was tweaked or taken out. Michael became Markl, the black door lead not to war but to Wales, and Suliman went from being a missing man to a present, threatening woman. The book is certainly an enjoyable read, although at times, a little hard to draw together the finer details (I am a bumbling reader, though, and consider that more my problem and not altogether a problem of story). My conclusion was that you can't lump the two together. The anime is so distinctly Miyazaki.
Howl's Moving Castle has all of Miyazaki's hallmarks. That strong female with (eventually) short hair, a nod to nature, and a very strong anti-war message. It interested me that the two plots were almost an inversion of one another. War wasn't a looming environmental factor in the book; it was probably mentioned three or four times, outright only once. Yet in the movie, it was the driving environmental factor, and most of the plot got tangled up in it. Important points, like Sophie being able to break her own curse, and Howl's and Calcifer's contract, remained intact. I had read when doing research for my thesis that Miyazaki had stepping into the film project after the previous director left and rewrote the whole thing. I never knew how much he had rewritten until I finished the book.
Another intriguing point was that images that I found a little creepy in the book were altogether gone in the film. Turnip the scarecrow was pretty genial in film. He's helpful and well-liked by the other characters. In the book however, he was a bit frightening and freaked out anyone else who happened to be around. Calcifer was much more menacing in appearance in the book than in the film. Thinking through the movie, Howl might have been the scariest character, or blob men. But that's your call.
I usually like movie adaptions of books. Sometimes I may not agree with their editing choices, but I generally understand why people do what they do in film. What it comes down to is that Howl's Moving Castle as a book is nothing like the film (and vise versa) except at its bare bones level. Sometimes with movie adaptions and their books, you have to choose which one you like better. But that's definitely not the case with this particular set.