This week: Bernard Crick explores Middle Britain: Jana Howlett unmasks the KGB; Kate Saunders on mad poets. Plus: win a trip to Italy; Geoff Dyer's continental shelf of books on travel, place and memory now includes a Parisian romance. Gareth Evans profiles a restless spirit of the age
At a recent concert, the great British jazz pianist Julian Joseph described life as "an improvisation". He might have added that memory could be seen as its retrospective score. Such sentiments offer a useful point of departure for the literary progress of Geoff Dyer. A tall, soft- spoken Europhile, born in Cheltenham in 1958, Dyer has over the past 10 years developed a prose style that can just as easily accommodate fiction as essay, autobiography as social history. He has written seven restless, nomadic books, all of which have strayed in various ways across literary borders. Taken together, they show that there is strength in diversity and much to be gained from exploration at the edges of genre and experience.

Both in his books and his wide-ranging journalism, Dyer mines a fertile seam that runs from experiment with structure through to a sly and subtle respect for established models. He started out, more or less conventionally, as a freelance journalist for magazines, but he has since then resisted the assumptions behind the construction of a literary "career". Dyer questions the concept of specialisation, runs with his instincts and enjoyments, and moves effortlessly from pan to zoom.

Yet there is clearly a Dyer "project" - a larger schema behind his disparate choice of subjects and modes. A tone of purposeful drift in his books mirrors the discipline of the process of their writing. His books are humanist texts, rife with ideas. But they can be read essentially as place, time and motion studies: road-books of the heart and intellect.

Like his chief mentors, D H Lawrence (Dyer's idiosyncratic reading of the novelist, Out of Sheer Rage, appears in paperback soon) and the maverick genius of Euro-letters John Berger (the subject of his first book), Dyer has long debated the question or "problem" of England. More often than not, he has found the answer abroad. In this respect, he has followed in the long and honourable tradition of British writers who crave the departure lounge rather than its suburban equivalent.

Dyer's restlessness, however, possesses a distinct quality. Movement both real and internal (the footfalls of the spirit) courses at the centre of his work; whether he trudges alongside the First World War troops for The Missing of the Somme, stalks Lawrence's constant shifts, or improvises into fiction for his extended riff on jazz, But Beautiful (which is reissued in May).

The counterpoint to movement is a sense of place: in Dyer's opinion, the usual trigger to his writing. What completes this trinity of deep impulses at play is the potency of memory - time as it operates in space, the after-image of experience. Dyer both celebrates and exorcises the products of memory. If his project needed a label, the title of his first novel - The Colour of Memory - would serve as well as any. Triangulating these three prerogatives, Dyer maps his literary and personal trajectories. Paris Trance (Little, Brown, pounds 9.99), his latest excursion into fiction, is no exception.

The title suggests the exotic displacements of Wim Wenders's hobo epic Paris, Texas - that same cinematic sense of image, of dislocation, of sudden juxtapositions and the discovery of the luminous "other" within everyday imperatives. In spite of a warning not to trust the book's geographical coordinates, it is obvious that Dyer does know the place. There is a real sense of an achieved topography to the prose, and yet his caution is valid. The book is only the most recent in a long and distinguished series of fictions of the city (by authors such as Louis Aragon and Andre Breton), in which the great dream of Paris is constantly worked upon and tested for resilience.

Dyer raises the spirit of Scott Fitzgerald, and he takes the briefest of extracts from Ernest Hemingway's Fiesta. These are not grand mission statements, however, but the banal (and transcendent) ephemera of things glimpsed or overhead at cafe tables and in parks. Dyer borrows a remark from Lawrence on the redundancy of plot, and looks through the celluloid- tinged eyes of his four protagonists: twentysomething voluntary exiles, paired off into affection. He then offers a song to the jazz of city living, with its epiphanies of rain and its small, daily victories.

Forsaking chapter breaks for short, white breathing-spaces, the book espouses a philosophy of moments. Dyer is particularly telling on the urgencies of youth, the anticipation of new and familiar pleasures, the rituals of urban encounter, and the ebb and flow of relationships. There is the wonder of granted access to another's space and body; the delinquent harmonies of male friendship; the rush of group violence.

The psychology of character has a delicacy and easy grace. A warmth in the descriptions of sexual exchange make this one of the few books able to speak convincingly, without sentimentality, of a certain kind of contemporary joy - one framed, unusually, within the limits of monogamy.

Indeed, outside its pop-cultural references, its Tarantino-esque exchanges, and its topical narcotics, this is an endearingly old-fashioned book. It asks the lasting questions about how to live, how to belong, and how to balance the pursuit of hedonism with the gravity of a growing responsibility. This is a slacker Bildungsroman, if you will.

A skilfully crafted map of the human heart, Paris Trance only stumbles when it attempts an explanation of the reasons behind the decline and fall of Luke, one of the four, and a would-be novelist. A man who does not exist outside others, Luke is divorced from the trajectory of his life, despite attempts to move from the fringes to the centre of his own being.

If the somewhat hurried reportage of his collapse does not ring clear, it is less through a failure of insight on Dyer's part than a result of his generosity towards the character's weakness. Since memory is the bridge here, and because the book at times displays an almost Proustian reverence for the past, it makes Dyer's decision to split the ending between two climaxes - one formal, one chronological - all the more effective.

We leave the book in the sublime immanence and permanent present of a dazzlingly calm and hot summer's day. The "trance of longing" for a life so fully experienced that it passes beyond the need for remembrance remains intact, and is temporarily attained. In a world of light, where sky is the only distance, Luke realises his ambition. Meanwhile, we acknowledge Dyer's insight into the qualities of time; and Paris Trance takes its place with his other books on that continental shelf where the water darkens and the ground begins to give as deeper currents carry us to different shores and ports.