It's an excellent book, as are all Philip Reeve's novels for young persons.
His other stuff is a series set in the future, but with a steampunk feel. I've read the first three and look forward to the fourth coming out in N. America.
The news about the movie is great, too!
If VSF for kids really takes off, it will certainly help my own series: book two, "The Faceless Fiend" went to the copy editor today.