One of the best WWII movies extant. Based on Cornelius Ryan's book of the same title it is, unlike many movies, very accurate in time, detail, personalities and tactics.
Cornelius Ryan also wrote two other equally good books: "A Bridge too Far" and "Enemy at the Gates." All three of his books are worth the time to read. A Bridge too Far was also made into an outstanding movie. If you're a former Para, you'll love the jump scenes in the movie. I believe the British Airborne Regiment did the jumping in the movie.
An interesting piece of trivia: Sean Connery went from a corporal in "The Longest Day" to the First Para Division commanding general in "A Bridge too Far."