I actually finished reading this late last night. Naturally, I was too tired to write a review, but from now on I'm going to do my best to, once I turn the last page of a given book, write a review immediately. I have to do what I can to fight my procrastinative nature (not sure that's a word, but whatever).
My reason for picking this book up is that I absolutely loved the animated film version, directed by Hayao Miyazaki. (I embedded a trailer at the bottom. Although the book wasn't bad, I think I would have been better off if I hadn't seen the movie beforehand, because I kept thinking of how awesome that story was, and the book just couldn't live up to it. ~,~
The book and the movie couldn't have been more different. Well, at least the beginning answered a lot of back-story questions I had while watching the movie. But everything that follows Sophie (the girl cursed with old age) entering and becoming a part of Howl's castle was absolutely nothing like I expected would happen. There are a couple added characters and scenes in the plot, and nearer the end I believe it became almost episodic. Like the Time Quake, the conclusion only came in the last chapter, and it was much too quick and happy to be entirely satisfying.
So my advice is to not necessarily read the book at all and just check out the movie, because that is truly awesome, engaging and rewarding story. However, if you're honestly curious and want to give the book a try (it isn't all that bad, after all), I suggest reading the story before you view it, because then you can appreciate how much better the movie is. This is rather than experiencing it the way I did, having the movie in my mind and getting let down by the book.
Posting this review has made me realize that I've forgotten to embed trailers of movies based on books I've read in a few reviews. I'm going to fix that now...