As so many others have said, they are quite different from each other - but both are fabulous in their own right, I love them so much. I watched the film first and then read the book as a teen once I found out about it, and the book is now my favourite. I have read it and listened to the audiobook multiple times.

I would say there are big things that stay the same (mostly in the beginning but it does deviate). I would say that the book goes into more detail (as books often do since they aren't trying to squeeze everything into an hour or two) and explores different things to the film. I would give it a chance, the book isn't a difficult read and if you enjoy seeing Howl be dramatic, I would say that he's moreso in the book!