We have met Alexander Cleave, the narrator of Ancient Light before. On the first occasion, a dozen years ago, in John Banville's novel Eclipse, the actor, on the run from catastrophic stage fright and his wife, pitched up in the abandoned home of his dead parents and tried to come to terms with some of the ghosts of his childhood. In that novel the spectres of Cleave's anguished state took on strangely corporeal form: a ghoulish caretaker and his wayward daughter haunted either the ramshackle house, or the upstairs bedrooms of narrator's mind; the reader was never quite sure which. Eclipse was very much concerned with the escape hatches of memory, the immanence of past lives that we use to block out the present. The shades of Cleave's ghostly dream world on that occasion were brought to an abrupt close by news of the suicide in Italy of his only daughter, Cass, haunted by demons of her own (a story that itself was embellished and inhabited in Banville's 2002 novel, Shroud).

In the opening pages of Ancient Light, Alexander Cleave is back on his journey of self-absorption, a decade on from that defining tragedy. He is in an upstairs attic room, apparently writing a memoir of first love, while downstairs, some nights, his wife sleepwalks desperately from room to room in restless search for Cass, before he guides her back to the marital bed. His own grief takes on a different form: he seems to have retreated into the mostly consoling memory of a passionate teenage affair with the mother of Billy Gray, his best friend. Cleave is 15 in his head, wilfully turning back 50 years, in the quest "to fall in love again, to be in love again, once more". His is a theatrical voice, and as before, through its self-dramatising filter, we are never quite sure where we stand: "Some say that without realising it we make it all up as we go along, and I am inclined to credit it, for Madame Memory is a great and subtle dissembler"

What follows  a breathless account of Cleave's first charged and fumbling encounters with the woman 18 years his senior  becomes far more real than anything that happens in the present surface of the novel, the day-to-day anguish of bereaved parents, and, latterly, the unlikely renaissance of the actor's career in a filmed biopic of a controversial literary critic. The recovered fantasy of teenage lust, or love, apparently wipes everything else clean. Mrs Gray's anatomy is conjured with such poetic fervour, and tangible fleshly desire, that the ghosts of the now seem pale and insubstantial things.

Banville, with his forensic sensory memory, his great gift for textural (and textual) precision, his ability to inhabit not just a room, as a writer, but also the full weight of a breathing body, is exactly in his element here. Cleave begins with nothing much more to go on than the vision of a woman on a bicycle half a century ago, with "all the dash and grace of a trim schooner plying fearlessly into a stiff nor-wester", inadvertently revealing a momentary glimpse of "taut suspenders and pearly-white satin knickers". The woman may or may not have been Mrs Gray, but he likes to think so, and from that moment of awakened desire, he tells himself, all of the rest of his life has flowed.

Once Cleave is into this fantasy  interrupted only occasionally by his wife knocking at the attic door, interventions that he rebuts by shielding his words with his arms, cradling his memory, like a swot in a maths exam  nothing gets in his way. After a first chance encounter with Mrs Gray naked in a dressing table mirror, no end of trysts and couplings are recalled, or conjured: in the back seat of her husband's car, in the abandoned shack in the woods Cleave used to play in with her son, in the dim-lit rooms of her house, hung with laundry, where all the imagined mysteries of Mrs Gray's 33-year-old form are revealed to him in their intimate wonder.

As the inevitable tragedy of this lost innocence unfolds in his narrator's mind, and detail piles on detail, the lost buttons, the "hot slack mouth to kiss", from time to time Banville taps his reader on the shoulder, just to undermine the rapture a little. A strange and barely believable subplot takes root in which Cleave the actor appears to abscond with his leading lady, Dawn Devonport, in the film in which he is supposedly starring. The character he plays in that film, Axel Vander, the literary critic, is not only a near anagram of his own first name, but also, Banville readers will recall, the curious protagonist of Shroud, in which his life crossed catastrophically with that of Cassandra Cleave. If all this makes it sound like a circle is about to be closed, don't be fooled. Cleave takes most of his clues to playing Vander, who seems to be a cipher for the post-structuralist Paul de Man, from a book by a Mr Jaybee (JB, geddit?) with which with he struggles to get on.

Banville's three novels taken together are not so much a trilogy as a triptych mirror, like the one in which Cleave first spied his Mrs Gray undressing. Not much is resolved between them, though each one creates a vivid new angle of reflection. Banville's ostensible theme throughout might be the fictions we tell ourselves in the name of memory, the self-protection and the self-harm that the past affords us, but they never threaten chilly abstraction, or even formal riddling of the kind favoured by Paul Auster. His writing is too precise, too beautifully freighted with the described world for that. Cleverness is on display, and nothing might be quite what it seems, but Banville's duty of care, to the emotional lives of his characters, to the worlds in which they live, is not neglected for a moment.

It is a decade since John Banville's novel Shroud narrated the events that led up to the death of the painfully disturbed Cass Cleave, who threw herself from a church tower on to the rocks below in the Ligurian coastal town of Portovenere. Shroud was a continuation of sorts of Eclipse (2000), which imagined the return of classical actor Alexander Cleave, Cass's father, to his childhood home after a professional catastrophe. Subsequently, Banville wrote two further novels, including the Man Booker-winning The Sea, as well as inventing an entirely new writing persona as Benjamin Black. Now, in the third novel in this loosely configured, frequently achronological series, we are with Alexander again. Once more, he is excavating his distant past, on this occasion the teenage affair he had with Mrs Gray, a woman 20 years his senior and his best friend's mother; he is grappling, always, with the aftermath of Cass's death and with a grief that ceaselessly reconstitutes itself; and he is preparing for an unexpected reawakening of his career.

That is perhaps the barest summary that one could hope to achieve of Ancient Life, a novel criss-crossed with ghost roads and dead-ends and peopled by shifty characters who seem provisional even to themselves. It is written in Banville's customary prose, rhythmic and allusive and dense with suggestive imagery, prose that deliberately slows you down and frequently wrongfoots you. It is not a way of writing that is beyond satire, even by its own creator, as a passage about a third of the way in suggests. Cleave has been approached to play the part of the late Axel Vander, a notorious and disgraced literary theorist who featured heavily in Shroud and who bears a certain resemblance to Paul de Man. The project is a film entitled The Invention of the Past, and it is based on a biography of Vander by a writer called "JB", a man Cleave describes as "distinctly odd", who "grows odder each time I encounter him". Reading the book for research purposes, Cleave finds himself staggered by its style: "Rhetorical in the extreme, dramatically elaborated, wholly unnatural, synthetic and clotted, it is a style such as might be forged  le mot juste!  by a minor court official at Byzantium, say, a former slave whose master generously allowed him the freedom of his extensive and eclectic library, a freedom the poor fellow all too eagerly availed himself of."

The witty self-deprecation here is probably sincere  Banville has said in a Paris Review interview that he loathes his fiction and finds it an embarrassment  but it is also, one suspects, a complicated retort to his critics; in the same interview, he confessed himself bewildered by people who find his novels detached from real life, distant and unemotional. "To me," he said, "my books are completely realistic. They're the world as I see it."

That world is one of collapsed time, in which the "gradual shipwreck" of life exists alongside the memories  albeit faulty and elusive  of a past that seems far more intact and filled with possibilities. Consequently, Alex's clandestine romance with Mrs Gray is portrayed as a liaison that, despite the impossibility of its being made public or enduring, follows simple imperatives and delivers straightforward pleasures: "Certainly she granted me full freedom of her body, that opulent pleasure garden where I sipped and sucked, dazed as a bumble-bee in full-blown summer." For 15-year-old Alex, it is, of course, a threshold beyond which adulthood beckons, but his impulses and emotions are still those of a child: when he is thwarted by Mrs Gray, he rages at her petulantly; at other times, she slips back into being simply one of the adults, allowing him to tell her boyish fibs and elude her authority.

Adulthood is not so easily navigable. Now in his 60s, Cleave struggles with the idea of passing from one place to another; he and, he suspects, his wife Lydia, are both beset by fears that their daughter "did not fully die but is somehow existing still"; he is compelled, later on in the novel, to undertake a literal journey to Portovenere, but is unable to cross the final strait to the exact location of her death. In that unfulfilled mission, he is accompanied not by Lydia, but by an actor who is and is not a daughter substitute; also bereaved, she has recently failed to commit suicide, apparently halted by a similar diffidence in the face of boundaries from which one cannot return.

The actor, Dawn Devonport, is one of several characters to emerge from the narrative gloom without ever fully making themselves known, the most notable of whom is Billie Stryker, a "researcher" on the film who comes to seem part psychotherapist and part savant. "To talk to her," notes Cleave, "is like dropping stones into a deep well," but it transpires that her function is to enable him to talk about himself and then, like a dramaturge, shape her discoveries into some kind of narrative action. From time to time, even more shadowy figures loom into view: a lugubrious night porter in a hotel made up of corridors and vestibules; a mysterious guest who confides that he is in mining ("'Underground,' he whispered") before warning Cleave to be aware of jealous gods.

The effect of the dual narrative  its forays into a past that we know has been truncated, and probably violently, are regularly punctuated by Cleave's dream-like, unstable present  is disorienting. At the novel's beginning, they seem unconnected, save for by their subject; by its close, the past seems entirely inflected with the present, both studded by weirdly disrupted and recast parent-child relationships. Its future is set to continue, as Cleave prepares to undertake another quest in order to mount a fresh assault on the mysteries that surround his daughter's impenetrable mind and her as yet unknown end. As much, however, as he presents his search as one for concrete answers, it is another question that hangs over the whole enterprise, both his and, indeed, Banville's: "Since it seems that nothing in creation is ever destroyed, only disassembled and dispersed, might not the same be true of individual consciousness? Where when we die does it go to, all that we have been?"