It's very Gothic, with the skyscraper taking the part of the castle, and there being a definite almost Gormenghast element to the way there are worlds within its concrete structure. One of these is a pre French Revolution style garden that sits at the top of the skyscraper. It serves as a perverse Versailles for the richer tenants, who have access to light, one of the most important commodities in the high rise; poorer families lack access to light, even if they do have all the other amenities they could imagine.
Into this world comes Laing, our protagonist, our untouchable. I can't comment on the book yet as I haven't read my copy, but in the film Laing is an everyman, in the sense that there doesn't feel like he has much personality, you'll note in the trailer someone says 'I thought you were empty', He stands as an observer, an outsider in a world of debauchery. In many respects he is innocent, sunbathing naked on his balcony without a care in the world. The film sees him inducted into the world of the high rise by way of casual sex, parties, and drugs. He never quite fits though and the high rise somehow never feels like it's his home; he doesn't even unpack and seems to live off coffee. You get the sense that something is wrong with him, be that in the form of his choice of paints, turning his apartment grey. It's as if he is seeking to hide himself from us, a situation that only grows worse as the film progresses and he acts as a go between for both the Ancien Regime at the top of the tower, and the partying residents who eventually revolt against the 'natural' order.
The issues come in the form of amenities breaking down, power cuts are common and as dissent grows in the lower levels all out war blossoms. Riots become common and as the society breaks down we see a splitting of the tower along gender lines, with the women and children banding together as the men become dangerous. Rape isn't shied away from, though the film does deal with it discreetly. Other issues, violence and murder, are more blatantly dealt with, while the sexual tone is crude and animalistic. This all feeds into the central message of how close to the surface our beasts lie.
The film's imagery very much references the idea of rot lying under the surface, whether that's Laing demonstrating how to skin a head to examine its brain, or the row of rotting peaches in the supermarket with its permanent offers on French goods.