Richard Linklater’s new comedy isn’t a biography of Orson Welles – based on Robert Kaplow’s bestselling novel, it portrays the late, great director at 22, brimming with confidence and a furious desire to take Broadway by storm – but it captures his larger-than-life spirit, the hubris of an artist reaching the height of his creative powers and fully aware of it.

The film is set in 1937, a week prior to the opening of Welles’ innovative reimagining of Shakespeare’s Julius Caesar with the Mercury Theatre players. Richard (Zac Efron) is a fresh-faced rube, hired by Welles on a whim and thrust into the role of Lucius, which requires a strong set of pipes, a familiarity with the ukulele and the moxie to act opposite the director himself, playing Brutus.

Richard fibs his way into the part – his ukulele skills are rudimentary at best – but Welles (Christian McKay) is too preoccupied with rewriting the Bard to care. He is a perfectionist, a micromanager in the truest sense, who slaps down all challenges to the resident genius. As Welles tells his actors, he owns the house, and anyone foolish enough to cross him will be shown the door.

Is Welles a tyrant? To the extent that he bullies his cast, creating as much drama off stage as on, he is. Yet he knows when to build his actors up, massaging their egos just enough to keep his production from coming unglued. (In all his underlings he sees “images of magnificence,” or so he tells them.) He’s not out to make friends, but even his most strident critics can appreciate his devotion to craft. He aspires to greatness, and demands nothing less from the help.

Me and Orson Welles is transcendent when Welles commands the stage as he did in 1937, four years before directing his first feature film, Citizen Kane. He is the stellar attraction in Kaplow’s coming-of-age story, which traces young Richard’s hot-and-cold romance with the theater.

McKay, who previously starred in a one-man stage show as Welles both in his prime and his declining years, is a revelation here, with a performance both fearless and mesmerizing. This is a man who has done his homework. He captures the director’s mannerisms, including his incomparable rumbling baritone, with uncanny precision. But to describe McKay as a master impersonator would be an injustice. He is channeling a prodigious spirit here, and his work should put him in the first rank of Oscar contenders.

That’s not to marginalize Efron, the High School Musical star saddled with a character hopelessly lost in Welles’ shadow. Richard is, in effect, our blank-slate narrator, a witness to the occupational hazards facing every actor, whether a veteran like Joseph Cotten (James Tupper, perfectly cast) or a 17-year-old neophyte from New Jersey. After his relationship with Welles takes a bittersweet turn, Richard contemplates leaving the stage for good, but no matter – he is young, handsome and hungry, with a future full of promise.

The same can be said for Welles, who would establish his legend on the big screen with Kane and The Magnificent Ambersons (1942). Yet in his uncompromising approach to his work – the audacity that earned him so many accolades – we see the very qualities that eventually made him an albatross.

Welles, whom Linklater has called “the patron saint of indie filmmakers,” would be defeated, if not humbled, by Hollywood studios that quickly tired of his expensive movies and meager box-office returns. (Before his death in 1985, he concluded a storied but ultimately shipwrecked career as the voice of Unicron, a planet-eating robot, in Transformers: The Movie.) Me and Orson Welles affectionately recalls his glory days, when Caesar was the toast of Broadway and the director’s creative fire burned unabated. If the Richards of the world happened to get singed, well, that was show business.