"There are two kinds of pity," writes Stefan Zweig in his only full-length novel. One helps only the pitier. In feeling for someone, they make themselves feel better. The other sort, he says, "stand[s] by the sufferer, patiently suffering too, to the last of its strength and even beyond."

It's a lesson we theatregoers, sobbing in the stalls, would do well to remember, and one Zweig drills into his readers. Lieutenant Hofmiller, the young cavalry officer at the centre of Beware of Pity, lets the wrong kind of pity run away with him. Each time he does, acting to alleviate his own inner guilt, he digs himself deeper and deeper. Each delays the inevitable fall-out, and makes it far worse in the long run.

Hofmiller's quandaries start with a faux pas. Invited to a society ball, he asks the host's daughter Edith (Marie Burchard) to dance, only to realise – mortified – that she's partly paralysed. To make up for his mistake, he befriends her, in part out of pity. His house visits stave off his guilt, his charity feels good and sowing false hope, first of a cure, then of a relationship, feels even better.

Hofmiller's problem, his fatal flaw, is his inability to detach himself from his situation. Feelings dictate his actions and, every time, emotions get the better of him. Simon McBurney spins that into most total theatre. He floods the stage with feeling; flushes every moment with sights and sounds and sensations and signs and so pulls us this way and that. We see nothing objectively. Everything's oversaturated; all tone and all too much to take in. It's confounding, overwhelming and, ultimately, manipulative.

When Hofmiller sees Edith stand for the first time, for example, the stage picture splinters. She's helped to her feet and time slows to a still. Strings screech, glass shatters on a screen, and, in slow-mo, her limp becomes agonised and monstrous. The narration spools, "she stoops like a witch," and a ballerina bows and pirouettes in projection, beautiful and transfixing. Hofmiller's heart thumps over it all. He – and we - fall into "an abyss of feeling" and Edith's affliction seems the worst thing in the world.

Don't forget McBurney is a maestro at this sort of thing. He has the most acute sensibility for theatrical tone; a conductor's sensitivity to rhythm and timbre. When Hofmiller tries to hold strong, as he's begged for good news, strobe lights and slow-motion catch all his horror. Silence aches like a stomach knot until he capitulates. Elsewhere adrenaline rushes come with racing oboes and whooshing trains, and relief blossoms with twinkling pianos. Strangers chew loudly on chunks of bread, spitting crumbs as they speak, and trusted friends seem to sway in sync as they take walks together. At all times, the feelings distort the facts.

If Zweig cautions about getting too close, though, McBurney also warns of the dangers of distance. This is as much a memory play as The Glass Menagerie, entirely narrated by an older Hofmiller (Christoph Gawenda), but more than that, it's a series of stories in stories. One key incident passes through four different tellers: it's confessed, recounted, remembered and, finally, related to us here and now. McBurney shows us the whole chain, and lets Chinese whispers set in. What, he asks, can we really trust? Neither what we're told, nor what we feel. As Hofmiller, Laurenz Laufenberg mostly stands still centre-stage, as paralysed as Edith. It's no wonder that, in the end, as war breaks, he just does what he's told. Without facts, we become followers.

Beware of Pity is not an easy watch. In fact, it's exhausting; two hours of theatrical barrage, of fragments that need piecing together and Russian doll fiction. It is, however, an illuminating explosion of Zweig's story, which can so easily seem slight and sentimental. Not only does McBurney extract its philosophy, he sews that back into our own world: our pity towards suffering we only see from afar; our disorientation in a post-truth world, where media manipulates and feeling overrides fact; and that sense that history might be repeating itself. Beware of pity, indeed.

Beware of Pity runs at the Barbican Centre until 12 February. The final performance will be live-streamed on Complicite's YouTube channel and will remain online until 26th February.