As TonyInterruptor begins, musician Sasha Keyes is in the middle of an improvised trumpet solo. A man stands up in the audience and says, “Is this honest? Are we all being honest here?” He points at Sasha and adds, “You especially.” Soon a video of the episode appears online, with a companion clip of Sasha’s vitriolic reaction: “Some random fucking nobody … some dick-weed, small-town TonyInterruptor.”

Given the times we live in, this naturally leads to Sasha’s trial by social media for artistic fraudulence and abusive conduct. But the shockwaves soon extend to everyone adjacent to the event: Fi Kinebuchi, the self-styled “Queen of Strings”, who was playing with Sasha at the time; India Shore, the teenager who posted the first video; India’s father, Lambert, an architecture professor with a secret crush on Fi Kinebuchi; his wife Mallory, who divides her time between parenting her daughter, Gunn, who has special needs, and venting intellectual spleen; and even to TonyInterruptor himself, real name John Lincoln Braithwaite, an otherworldly outsider whose “main occupation – his duty, even – is to observe and assess the falling and the catching of light”.

The author of more than a dozen books, including the Goldsmiths prize winner H(a)ppy and the Booker‑shortlisted Darkmans, Barker is known for experiment and brainy whimsy. There could be no better person to write a comedy about art and its discontents. The novel is devastatingly on the money about the ways we’re all not being honest here: whether as flawed, self-conscious humans, or in the special case of artists, who strive harder for honesty and thus fall harder into affectation. Even the unworldly Braithwaite isn’t immune. What are we to make of a man who smokes because “smoking is a condensed and bastardised form of fire-watching”, and when asked to shake hands responds with, “I object to handshaking on ideological grounds … but you seem well-meaning so I’m happy to respond in the vernacular you’re most comfortable with.” Sincerity here is just the youthful illusion that we’re exempt from universal impostordom; or the lovely illusion of lovers that their inamorata is the one in a million who is really real.

The characters’ sensitivity to the falseness all around them – and in them – gives them no peace. Lambert describes his wife, Mallory, as relentless in her criticisms, “like a seagull up to its knees in sea-swell, determinedly dissecting a crustacean as it rolls ceaselessly back and forth”. But this is true in various ways of all the characters, who are always finding fault. Sometimes this means railing at others, as when India tells her dad to “stop always making everything so … so INTELLECTUAL, so META … and just … just … for once in your life risk being real”. Sometimes they bemoan their own artificiality, as when Lambert conceives of himself as being “like a Moneymaker tomato: ripened to an unnaturally bright hue on a constant drip-diet of Baby Bio”.

The prose is a profusion of thoughts and associations, and shadings of the thoughts, and metaphors extending from the associations. All this is delivered in long, manic sentences that love to chase their own tails. When we’re told Braithwaite is “like a leading character in a bad 1980s American capitalist drama (say Dallas: the over-indulged younger brother, the prodigal son who returns to the oilfield and promises his tough yet paradoxically indulgent slate-eyed, tan-faced father that he will learn the trade from the ground up; prove himself). But also like a character from an excellent, slightly clunky but extremely sincere first play about a demoralised primary school teacher who is struggling to nurture a gifted but troubled Irish Traveller child written by a 23-year-old northern prodigy whose uncle once ran (and possibly still runs) an abbatoir” – well, are we really expected to parse all that? I suspect not. The excess is the joke, and the joke is sometimes on the reader who struggles to get anything as sensible as an image out of Barker’s imagery. It’s a rollercoaster kind of excess, where the best part is that it’s too much. Sometimes, I think, we’re being invited to enjoy the slapstick experience of losing our footing mid-sentence, and to join the laugh if we fall flat.

Midway, the book takes a turn into romantic comedy, with a series of scenes where unlikely characters fall for each other. The honesty they’ve been pursuing, it turns out, consists not in improvised jazz, but in becoming besotted with an inappropriate person and blowing up your life. Barker manages this shift with an extraordinary lightness and perceptiveness, making it feel as though the rogue wave of love sweeping through her narrative was inevitable as soon as the words “Are we all being honest here?” were spoken. In a pivotal scene, a bewildered Sasha Keyes sums up all we’ve learned by citing the “Buddhist Lineage of Mis-steps”, in which it is the seeker’s mistakes and failings, not their spiritual achievements, that lead to enlightenment. It is a somehow fitting climax to a book in which Barker seems incapable of putting a foot wrong. This is satire that sees right through you, but forgives you and teaches you to forgive yourself. It’s that rare thing, a serious work of art that is also a giddy confection: a vehicle of pure delight.