By Paul Doro   Published Jan 17, 2001 at 12:22 AM

The general public does not like long movies. People are getting sick of sitting through three-hour films while at the same time they embrace 90 minutes of pure trash (see "Charlie's Angels"). It seems they are more entertained by mindless crap as opposed to intelligent films with something to say.

"Thirteen Days" faces an uphill battle. It's long, almost two and a half-hours, and everyone already knows the ending (but when you go to a romantic comedy, the same is true). Don't let that stop you from seeing it. It's a gripping and smart political drama that somehow never becomes boring.

In October of 1962, during the Cuban missile crisis, the United States came painfully close to entering a nuclear war with Russia. That's what you do know. The rest of "Thirteen Days" is a fascinating behind the scenes look at the decisions President Kennedy (Bruce Greenwood) had to make during those tense two weeks and the people who helped him.

The action revolves around three people: President Kennedy, his brother Robert (Steven Culp), then the Attorney General, and Kenny O'Donnell (Kevin Costner), an advisor to JFK and close friend of the Kennedy family.

Hollywood always stretches the truth, and "Thirteen Days" is no exception. The importance of O'Donnell's role is exaggerated, probably because a big movie star plays him. But the script by David Self, based on a book called "The Kennedy Tapes- Inside the White House During the Cuban Missile Crisis" by Ernest R. May and Philip D. Zelikow, mainly sticks to the facts.

Self and director Roger Donaldson ("Dante's Peak") make a good decision by beginning the movie with the discovery of the missiles in Cuba. It gets the audience involved and interested from the opening credits, and then never loosens its grip on them.

The cast, which is outstanding, is full of familiar faces. Greenwood was in "Double Jeopardy" and "Rules of Engagement." Culp is in the TV show "Jag" and had a small role in "Nurse Betty." Also excellent in supporting roles are Dylan Baker ("The Cell"), Frank Wood ("Small Time Crooks") and Kevin Conway ("Two Family House").

Costner is the weakest link in the cast. His Boston accent is forced and overdone. It's distracting at first but you don't even notice it after awhile. He gets points for effort, but sometimes less is more. Greenwood doesn't look much like JFK, but he gives a commanding performance. Culp, on the other hand, looks and sounds a lot like RFK. It should be a star-making role for him.

"Thirteen Days" may not surprise you much, but it's a story worth telling and a story well told. If you're not sick of long movies, and you enjoy a history lesson, you won't be disappointed.

Grade: A-

"Thirteen Days" is now showing.