Read the book
It's a fabulous film. Hopkins' performance is his best, far better than Silence.... The only one in his career that rivals it is Nixon. The book by Kazuo Ishiguro is even more beautiful and heart-wrenching than the film, so if you like the film, by all means read it. There is a fabulous scene at the end when the two principal characters part for the last time. Stevens cries and is comforted by a stranger on the pier.
I've read 4 of Ishiguro's novels. Besides this: A Pale View of the Hills, An Artist of the Floating World, and Never Let Me Go. The man is fantastic.