I watched the movie a few weeks before reading this book. I have to admit that I liked it a bit better than the book. It was one of the few exceptions where both - the book AND the movie - are great. I think this is only possible because the book is told in a very unique way. There are lots of pictures. But almost all of them are not there to illustrate the story but to actually tell it. They are great drawings which often look like a movie. I guess that's the reason why the movie is so much like the book: they could use those pictures and just had to build the scenes like the pictures. So reading the book was actually like watching the movie again!
The movie only has minor changes, which are usually for the better: the friendship between Hugo and Isabelle emerges earlier and the people working at the station play a more important role. In more opinion the characters in the movie are also more sharply developed.
What I loved especially about the book was that it has this unique combination of looking like a movie and having movies as it's chief topic. This is just great.