“Green Book” is the based-on-truth story of Dr. Don Shirley, a world class pianist who was booked to do a concert tour that included several dates in the deep south. Since this was 1962, and Shirley was African-American, he knew there might be trouble, so he hired a tough New York bouncer, Tony Vallelonga, to be his driver and bodyguard.

Viggo Mortensen is Tony, the working-class, less educated half of the duo. The actor gained what looks like about 40 pounds to portray this paunchy man who, despite his own prejudices, needs the money and accepts his place as the employee. Mahershala Ali plays Don as a cool, well-educated, disciplined man often offended by Tony’s words and attitudes, yet glad to have him along when they run into some tense situations.

The movie’s title comes from an actual book that was used by African-Americans during the segregation era to navigate through the racist south. It listed motels and restaurants where “coloreds” were permitted to sleep and eat, as well as entire towns that were to be avoided or put someone’s life at risk.

There’s a long history of opposites-attract road trip movies, all the way back to Clark Gable and Claudette Colbert in Frank Capra’s “It Happened One Night” (1939) and Veronica Lake and Joel McRae in Preston Sturges’ “Sullivan’s Travels” (1941). The list of classics in the genre also includes Jessica Tandy and Morgan Freeman in “Driving Miss Daisy” (1989), John Candy and Steve Martin in “Planes, Trains, and Automobiles” (1987) and even more recent works like Will Forte and Bruce Dern in “Nebraska” (2013).

Like those, “Green Book” takes diverse characters, throws them together in an us-vs-them partnership, and builds a bond between them. Both of the leads are excellent. Mortensen’s role is showier, but he doesn’t overdo it, while Ali brings a stoicism and determination to his. Linda Cardellini offers her usual fine support as Tony’s wife. It’s a bit of a departure for director Peter Farrelly, known for the broad farces he’s made with brother Bobby (“There’s Something About Mary,” “Dumb and Dumber,” “Shallow Hal”). Here, he plays it straight — although there are still several laughs along the way — and keeps the focus on the two men as they learn from and about each other.

The problem with the script (written in part by Tony’s son) is its predictability. While the chemistry of the two men works well — in an Oscar Madison/Felix Unger way — the racial stereotypes of the region are too obvious, right down to a fried chicken dinner, and there are two developments in the last 20 minutes that you’ll see coming from 20 miles away. That’s what differentiates “Green Book” from other black-and-white dramas of the past, like “The Defiant Ones” (1958, Sidney Poitier and Tony Curtis), or even the Richard Pryor/Gene Wilder comedies of the 1970s.

“Green Book” certainly pleased the audience I saw it with, and it won theĀ Audience Choice Award for Best Feature Film earlier this month at the 2018 St. Louis International Film Festival (as well as about ten others this year) — but I’m only giving it a 6.5 out of 10.