I was a little surprised when I discovered the book ends at the end of the first movie, and the flashback was the only thing Part II took from it. There are plot threads in the book that only really get paid off in the movies.
Red Dragon is okay but it's an example of trying to force greatness by stuffing heavyweight actors into every role. But Brett Ratner doesn't have greatness in him so it never quite takes off. Also Ed Norton is sort of bad in it.