IN the judgment of his brother Max, Günter Glass is "charmless, half-blind and fat." To Dean Angela Winterbottom, who comes to write Günter's life story, he is a "very great man, composed of many contradictions." Poor Günter: only 22 years old, a likeable innocent, a window cleaner, and already capable of polarising others' opinions of him to such an extent.

The anti-hero of Alex Christofi's entertaining and affecting novel, Günter finds himself in London, having become something of a minor celebrity in his native Salisbury thanks to to a near-mishap while replacing the aircraft warning light on top of the city's cathedral spire.

He had been very close to her mother Mathilda (it was she who had chosen his forename, seemingly prompted by a yearning for the abandoned country of her birth). But she had died before her time and, badly missing her habit of feeding him half-digested nuggets of knowledge, Günter had comforted himself with a surrogate in the shape of Wikipedia, "the greatest pool of half-digested information in the world."

He owes his addiction to syrupy Dutch waffles to his mother. To his father, a salesman who one day when Günter was young left him in a glass museum while he attended a business meeting, he owes his lifelong fixation with glass and his deep knowledge of its properties.

Thus equipped, he makes his way to London, having been invited there by John Blades OBE, a man who has cleaned half of the skyscrapers in London, and who is desperate to clean the vertical city that is The Shard.

Christofi's novel - he works as a literary agent and sometime Prospect magazine blogger - tracks the adventures of Günter in the capital. He helps Blades clean the IMAX in Waterloo; he has his first taste of romance, with a psychic and medium named Lieve; he worries about his widowed father back home, who seems to have gone to pieces; he has an uncomfortable lunch with Max, his deaf and abrasive younger brother.

He finds himself sharing a two-bed flat in Hackney with a hairy and faintly rancid German eccentric, whom Günter knows only as the Steppenwolf. This man is making it his life's work to complete a book - "a guide to living," as he explains to a politely attentive Günter. "An essential guide. Nothing extraneous." Blades, on the other hand, is a racist, and is given to propagating fascist theories, something that does not escape the attention of Günter.

Günter's life is narrated in the first person, but it emerges in the foreword that the book has been written by his friend, Dean Winterbottom of Salisbury Cathedral, the woman who had invited him to replace the aircraft warning light.

Winterbottom has couched Günter's story in what she describes as her "own brand of picaresque", and has invented characters here and there, but she succeeds in etching her friend's inner life so finely that we come to rather like him and to see him as a naive ingenue, but an endearingly optimistic one, too. We understand his sense of longing when he writes of his decision to abandon Salisbury: "I might live where skyscrapers defied the downward pull of time, standing out against the chaotic jumble of mere buildings. I might find someone to love and to make memories with, so that there might be some brief record of my existence..."

Then again, Günter is also the kind who makes himself a pot of coffee and some sugar-laden Dutch waffles then has to brew some camomile so that he can calm down.

Via Winterbottom's frequent footnotes, we learn that there is such a thing as an interrobang, "a tremendous typographical invention, used where a question is too loud or emphatic to expect that the speaker will listen to the answer." There are some very funny moments, too, as when Max and Günter insult each other by signing, when Günter describes the phases of his earliest years as "vegetable (0-1), animal (1-4) and memorable (4+)"; and when Max, while still at school, runs into an obnoxious classmate of Günter's named Karl, who boisterously queries Max's distinctive vocalisation: "There followed some unpleasantness during which both Max's ego and Karl's testicles were bruised."