A lot of people liked this book. I definitely recommend it for elementary kids... It's got sort of a pre-steampunk feel to it, lots of automata. Plus, it's about movies, and what kid doesn't love movies? There's a lot of good historical info included on the invention of movies, and it might lead kids on to other books. It's inventive, a lot of the story is told silently through pictures and that really suits the whole silent-movie theme.
That said, it didn't do much for me. It's just basic kid-book fare. The plot was painfully obvious to me and the characters were annoying, especially with their constant arguing over who should reveal secrets first. I was hoping for something mind-bogglingly wonderful from the praise it gets, but it was just the same old stuff: An orphan, a spunky girl to be his best friend, a mean old man, and a bunch of riddles to solve.
And- Hm. I really thought I had more to say about this, but I guess that's it. I recommend it, especially for kids, who won't notice that the story's been done so many times, but it's not a "heave it to the top of Mt. TBR" recommendation. A good similar book at a slightly higher reading level might be Chasing Vermeer by Blue Balliett, and some other books with the same general attitude are The Palace of Laughter by Jon Berkeley or The Magic Thief by Sarah Prineas (awesome, awesome book with review forthcoming eventually). Here's a list of books about the history of movies and one about silent movies, if this book sparks your interest.
Buy The Invention of Hugo Cabret