I think that it is fair to find different people who would answer the question in different ways.  I tend to think that the movie was far more positive and "happy" than what the note upon which the book concludes.  It seems to me that the reunion with his parents in the film is where the narrative ends.  Jim goes back with them and all is well.  Even though he cannot recognize them at first, he eventually does, they embrace, and the saga ends.  Yet, the ending of the book is much more complex.  The fact that the parents are enduring their own psychological horror in seeking to come to grips with their internment as well as Jim's own wrestling with the demons of his experience makes for a intricate portrait.  There is a great deal of post traumatic stress that is in both parents and child that is not evident in the ending of the film.  Jim's realization that he is of both realities, one in the past and one in the present is part of where his stress results.  The end of the book shows that Jim is at a state of being where "only part of his mind would leave Shanghai. The rest would remain there forever, returning on the tide like the coffins launched from the funeral piers at Nantao."  The book shows more of a realistic condition of surviving war.  The film's ending is positive and one feels good after it, but I am not sure that the same depth of emotion is evoked from it as is from the ending of the book.  In this, I sense a significant difference between both.