As he’s demonstrated in such films as Shine and the recent Broadway production of Ionesco’s Exit the King, there are few actors as adept at playing crazy characters as Geoffrey Rush. Now starring in the titular role in The Diary of a Madman, the performer delivers an inspired tour-de-force turn that plays like a demented vaudeville act.

Set in 19th century St. Petersburg, the piece depicts the lapse into psychosis of Aksentii Ivanovich Poprishchin, a low-level, pencil-pushing bureaucrat endlessly frustrated by the drudgery of his demeaning job. At night he retreats to the safety of his attic garret, where he pours out his increasingly bizarre fantasies into his journal. In between his exhausting exhortations, he’s attended to by his solicitous Finnish housekeeper (Yael Stone).

Decrying the dictatorial demands of his boss and indulging in his fantasies of an imagined love affair between him and the office director’s beautiful daughter, he regales us with such fantasies as the supposed dialogue between two neighborhood dogs and his dawning realization that he’s actually the king of Spain.

This production, which originated more than two decades ago at Sydney’s Belvoir theater company, is less effective as a dramatization of Gogol’s classic 1835 short story than as a vehicle for its star’s protean talents. Sporting a bizarre tuft of garish red hair and increasingly outlandish costumes, Rush delivers an endlessly physical performance in which his extreme bodily contortions provide a visual correlative to his character’s over-the-top rantings.

While the performance is certainly entertaining, neither it nor the dramatization—by David Holman, director Neil Armfield and Rush himself—ultimately cuts very deep. Although highly effective in conveying the comic extremities of the character’s eccentricities, it is far less so in its attempt to harrowingly depict his full-blown descent into madness.

Adding mightily to the show’s impact are its superb technical elements, including Catherine Martin’s set design with its blood red walls and claustrophobic green ceiling; Mark Shelton’s haunting lighting, which creates shadows that seem to take on a life of their own; and the evocative sound effects and music, created by a pair of musicians located at the side of the stage.

It’s a marvelous showcase, to be sure, for this supremely talented actor, Oscar nominated for his far more down-to-earth performance in the hit film The King’s Speech. But the production’s effects are all on the surface; at the end, we care far too little about this tragic figure, despite the undeniable laughs he’s provided along the way.

BAM Harvey Theater, 651 Fulton St., Brooklyn. 718-636-4100. Through Mar. 12.