There were elements of it that I found were better than the film and elements that I love more in the film. The film is much more gentler and more loving. The whole second half of the book is very different from the film plotwise.
I loved Sophie and Howl's bickering. It was a lot of fun to read. But then again I think I missed a bit more of the love that Miyazaki brought to his version. 
I loved some of the characters that were cut from the film. The whole sisterly aspect of it. I liked the scarecrow plotline better in the book than in the film where it does come out of nowhere really. I also loved seeing Sophie's magical abilities. I admit I am still unsure about the whole Wales/modern life aspect that really threw me off and didn't really fit with the story i feel. The ending felt a bit rushed. I did like the ending of the Witch of the West in the film more I think. But I really missed the most more of the romantic build up of Howl and Sophie. Like it felt too sudden while in the film it is much more gradual.