Here are 17 reasons to see “Oppenheimer”:

Cillian Murphy, Emily Blunt, Matt Damon, Kenneth Branagh, Florence Pugh, Josh Hartnett, Matthew Modine, Jason Clarke, Casey Affleck, Rami Malek, Tom Conti, Alden Ehrenreich, Dane DeHaan, Benny Safdie, David Krumholtz, Gary Oldman and Robert Downey Jr.

But here’s another reason that is even more important: Christopher Nolan.

The man who gave us “Inception,” “The Prestige,” “Dunkirk” and the “Dark Knight” trilogy is one of the few modern directors whose name alone brings folks to the movies — as indicated by “Oppenheimer’s” quarter-of-a-billion-dollar box office take.

It’s a handsome, gripping and brilliantly acted epic recounting the rise and fall of the man who oversaw the development of atomic weapons in the Manhattan Project. I initially could not figure out why Nolan chose this subject, and then I grew even more skeptical after noting the movie’s 180-minute run time.

Yet, despite its great length and unlikely topic, “Oppenheimer” cruises along in a most absorbing fashion. This is due partly to its cast and partly to switching back and forth between bomb-work at Los Alamos and two later hearings that would make or break the careers of Oppenheimer (Murphy) and Atomic Energy Commission honcho Lewis Strauss (Downey), who is gunning for a spot on Eisenhower’s cabinet.

Murphy and Downey are simply amazing — both clearly Oscar front-runners just now. In particular, it’s high time Downey snagged himself a statue, and the Academy won’t get a better chance than this.

But really, the entire cast is phenomenal, even if at first the countless familiar faces give a bit of a “spot-the-actor” feel. Krumholtz does his best work ever, and Damon is sensational as Gen. Leslie Groves, who tapped Oppenheimer for the work. Oldman, playing Harry S. Truman, submerges himself so thoroughly that his scene was half over before I even figured out it was him. (One negative note is that Truman — in my view one of this country’s finest chief execs — is presented as a bit of a caricature, which is terribly disappointing and not at all typical of this film’s general approach.)

But besides the cast, what feels most remarkable about “Oppenheimer” is how thoroughly it holds your attention, even though it has no action whatsoever — with the possible exception of the bomb-test scene. Through careful editing and his usual whiz-bang storytelling, Nolan keeps a steady but slowly accelerating pace that flags a little only toward the end; there, the double-hearing sequence, which keys on fascinating parallels between the two men, does slightly overstay its welcome. In the long run, the film could be about 20 minutes shorter.

It’s also a bit loud in spots, with too-strident music and ambient noise, both of which fight against Nolan’s fine dialog.

Here are some tasty samples from his script:

“Selfish, awful people — they don’t know they’re selfish and awful.”

“The truly vindictive are as patient as saints.”

A Jewish man, asked how long he’s been British, responds simply, “Since Hitler told me I wasn’t German.”

Later: “Amateurs seek the sun and get eaten. Power stays in the shadows.”

And here’s a widow lamenting her spouse’s commitment to the Spanish Civil War: “My husband offered up our lives to stop one Fascist bullet from landing in a mudbank.”

For my money, Nolan is as good as any director now working; he continues to carve out a career that ranks him with Spielberg, Frankenheimer, Wilder, Ford, Hitchcock, and Lang — I’m not kidding.

But even if you’re not a Nolan nut like me, you really should catch “Oppenheimer” if only to watch Downey work his magic.

And Murphy too. And Damon. And Oldman. And … well, I’m not going to list them all again.

Go see for yourself.