The film is based on a book about the true experience written by Ron Stallworth, a black rookie police officer who infiltrates the KKK in Colorado. (Lest the TV ads and film's title give the impression, no, he himself doesn't get personally inside. That's a joint undercover operation between him on the telephone and a white, Jewish officer.) John David Washington is excellent as the cop, and Adam Driver does a terrific job as his main partner. And there's a small, but wonderful performance by Harry Belafonte.
(By the way, some of the film's tension comes from the fact that Stallworth -- new to the job -- screws up and uses his real name when he makes his first call to the local Klan about joining. And so the undercover team is stuck with his real identity now being out there. It's a very funny moment, but one with very serious implications. Later on, Stallworth expands his reach and ends up becoming phone pals, by total chance, with the Klan's Grand Wizard, David Duke.)
It's important to note, too, that BLACKkKLANSMAN is not just a movie about what happened in the 1980s. Spike Lee is blunt here about racial hatred to and its connections to the current administration. There are clear slams at Trump throughout – a bit heavy-handed with the phrases, but a) in fairness, it’s sort of impossible to work in Trump phrases and not be obvious, and b) Lee doesn't overdo it -- since he doesn't have to. Say such phrases at only a few points, and you can't miss the point which pretty much of the audience has already figured out long before going to the movie theater. So, the use is blunt, but low-key. Until the very end, which was perhaps my favorite part of the movie, letting it all out and being as forthright about Trump as could be. I shall say no more. Other than it's all especially timely with it being the one-year anniversary of Charlottesville and the "very fine people."
Here's the trailer. It does a solid getting across the film, though the movie is significantly more tense -- and filled with the venal visceral language of the Klan members -- and therefore far-less "breezy" as it may seem here. P.S. The film's star John David Washington is the son of Denzel. You can fill in the last name.
And as a bonus video, here are Spike Lee and the real Ron Stallworth being interviewed on the show, CBS This Morning.