I couldn't help being amused by some of the differences from the film though (and, woah, there are MANY!). Namely, Howl. In the film, Howl is a tragic bishounen who fights bravely from the start. In the book, he's a Welsh drama queen who owns a guitar because it looks good and spends two hours in the bathroom every day. Actually, I find both versions of Howl adorable, but it's quite a change! Also, the whole plot makes complete sense and sheds a bit of light on the film's plot, even though the plots don't really match up.
And... I've run out of time it. Eep. Must dash!