”Incidentally, accidentally!” That’s how meaning — a heinous offense — creeps into a writer’s work, according to desperate scribe Katurian K. Katurian (Billy Crudup), whose grim and mostly unpublished short stories are the center of a child-murder case. The investigating officers (Jeff Goldblum and Zeljko Ivanek) represent a police state, and thus tend to eschew literature in favor of the sort of empiricism only electrodes can elicit. But The Pillowman, a gleefully uneven thriller from Martin McDonagh (The Beauty Queen of Leenane), quickly reveals intentions beyond the Kafkaesque. (”I don’t usually go in for –esques,” Katurian haughtily explains.) McDonagh absolves neither the artist nor the art, instead declaring both monstrous while celebrating the comic abomination of it all. It’s a metaphysical knot the playwright can’t quite untie, even in nearly three hours. But the cast — especially Goldblum, disciplining his Morse-code delivery — is having a ball.