Michael Keaton leads the charge as a teetering schizophrenic actor, struggling to find validation on Broadway after a long, expired run as a glossy Hollywood blockbuster-dweller.

On a purely technical level, it's astounding. Precisely edited to appear as though the whole thing were executed in one extremely long take, it's a mesmerizing experience, profoundly different and expertly crafty when the timeline needs to leap forward. It's dazzlingly acted, too, with Keaton delivering a masterful performance alongside noteworthy supporting work from Ed Norton, Emma Stone and (to my surprise) a very versatile Zach Galifianakis.

The moral lessons are laid on thick, though, and too often it feels like we're being lectured for daring to indulge in the kind of loathsome fun that drove our lead to this strange brand of mania. One scene in particular, Keaton's confrontation with a stuffy critic before opening night (who glares right into the camera before storming off in a cloud of self-righteousness) plays like a direct scolding of the audience.

Maybe theatre purists will take this as a firm voice of reason, the rare call of someone who finally gets it, but to me it came off as tremendously stuck-up and pretentious. I can't deny there's a lot to enjoy here, and it's a clear arrival for auteur Alejandro González Iñárritu, but I also can't help wondering how much better it would be without that permeating air of superiority.