A couple points (that I can think of): - The author of the webcomic/book was heavily involved in this movie. The book is more complicated (of course) and its storyline differs from the movie; the movie has a much more upbeat ending. They're different enough that generally the suggestion is to enjoy them both. There has been no sequel to the book (and I'm not really expecting one). - The studio(s) involved in this (Blue Sky and Annapurna Pictures) have been dissolved and no longer functionally exist.