So the trilogy is complete, and it is magnificent. The portrait of Thomas Cromwell that began with Wolf Hall (2009) and continued with Bring Up the Bodies (2012) now concludes with a novel of epic proportions, every bit as thrilling, propulsive, darkly comic and stupendously intelligent as its predecessors. “Concludes” is perhaps not the word, for there is no tone of finality. Cromwell, Lord Privy Seal, deputy head of the church in England, chief minister, second man of the realm, Cremuel to the imperial ambassador, Crumb to friends, has a great deal of business to do, through 900 pages, before we contemplate endings. The heights of his power are all before us, and though he likes ladders and cranes of construction sites, for his own progress he prefers to think of wings.

Bring Up the Bodies closed with bloodshed and wreckage. “But it’s useful wreckage, isn’t it?” and now Cromwell uses it, strenuously remodelling catastrophes as opportunities. Over four years, 1536-40, his tasks include the seemingly impossible. He must reconcile Lady Mary to her father the king, bring down two of the most powerful families in Europe, turn monks into money, prevent imperial invasion, organise a new queen. Taking opponents in his grasp like the snake whose poisoned bite he once survived, he must manoeuvre his arch-enemies the Duke of Norfolk and Stephen Gardiner. Cromwell lives these years with henchmen at his back, and guards at every door. “The times being what they are, a man may enter the gate as your friend and change sides while he crosses the courtyard.” As for clothes, best try a reversible garment: “one never knows, is it dying or dancing?”

We can already tell the shape of this book. We see that the crowd dispersing after Anne Boleyn’s execution in the opening pages (“time for a second breakfast”) will gather again at its close. Working with and against our foreknowledge, Mantel keeps us on the brink, each day to be invented. “Scaramella’s off to war,” hums Cromwell, a tune from his Italian youth. You need a war-song to go into dinner. This is what it’s like to be at the centre of power in Tudor England, and also a particular understanding of what it is, anywhere, to be alive.

Portrait of Sir Thomas Cromwell by Hans Holbein the Younger, 1532. Photograph: Ian Dagnall/Alamy

The Mirror & the Light is generously self-sufficient – to read this alone would hardly be skimping: it is four or five books in itself. But it also continues, deepens, and revises its forebears, negotiating with its past as does Cromwell with his. A spring lightly touched opens corridors into earlier books. Unlock the “room called Christmas” now and its past leaps out: this is where the doomed lutenist Mark Smeaton shrieked through the night among festive decorations that appeared, in his terror, as implements of torture. We know our way around Cromwell’s home Austin Friars and what these walls have seen. “My past pads after me, paws on the flagstones,” thinks Cromwell, who builds new houses and watches old ghosts enter. He knows the power of palimpsests. His Reformation involves the whitewashing of walls, but he sees how old faces show through from underneath. The Mirror & the Light is startlingly fresh in every moment, a new-made story with predecessors close enough to bleed through the pages.

Mantel’s Cromwell, now in his 50s, keeps the same daunting schedules as ever through 18-hour days. Lawyer, banker, chief diplomat, he is master of the grand scheme and every last memorandum. “Bear in mind,” he tells a friend and spy, “my field of interest is very wide.” He knows the price of wool and alum, and market values in the court’s “inner economy” of gossip and shame. He has drained the roads, reintroduced beavers, grafted better plums. And still his life depends entirely on Henry’s favour. Should the king die, or withdraw his love, all is lost. A moment’s inattention and the structure falls: hence the difficulty of sleep, hence the disaster of illness in which, through absence, one loses the advantage. “You are one man,” says Margaret Pole. “Who follows you? Only carrion crows.”

She is restating the terms of class warfare. The central conflict between the self-made blacksmith’s son and his aristocratic opponents (Norfolks, Courtenays, Poles) intensifies along with Cromwell’s power. As his chief of staff Wriothesley correctly observes, “The higher you rise in the king’s service, the more you mention the low place you come from.” His country, too, is obsessed by the relationship of class and power. The labouring rebels who march in the Pilgrimage of Grace uprising cry vengeance on the “vile blood” of any lowborn who tries to rule them. In Cromwell’s rearrangement of hierarchies, intelligence is all; those not clever enough to save themselves are not worth sympathy. Yet if he is the figurehead of a new meritocracy, he badly compromises his position as he funnels influence into his own family, bringing a new dynasty into being.

Though many readers have responded to the modern secularity of her fictional Cromwell, Mantel has always been firm about the strength of his religious conviction. Here she puts the evangelical cause at the centre of his life’s work. He is a heretic, and acts on it, risking everything for the gospel translation he wants to see in every parish and for his country’s alliance with Europe’s Protestant centres. Among the book’s most complex and fascinating subjects is the character of the Reformation that he passionately apprehends.

Modern times may sharpen our sense of Cromwell’s internationalism. If his England is to prosper, it must join every conversation across the courts and marketplaces of the continent. He employs in his household the best linguists to be found. As a boy in the kitchens of the Frescobaldi banking house, he was promoted upstairs for his quick wits and knowledge of the English used on the docks and streets; Wolsey employed him for his Italian; now he calls on ruffians and survivors from across the world to work for him.

Anne Boleyn is buried in the Chapel Royal of St Peter ad Vincula at the Tower of London. Photograph: Mrs Clooney/Getty Images

As much as this is a book about statecraft, international relations, class, faith and power, it must count, too, among the most penetrating studies of professional friendship: the complicated, unequal relations of masters and servants, tutors and proteges, kings and their ministers. “Henry and Cromwell. Cromwell and Henry”: they step apart from the court to talk alone, needing each other in desperate though different ways. Cromwell’s most vehement love and loyalty, however, belongs to a dead man, Thomas Wolsey: his teacher, employer and elected father. It is the quietest but perhaps the most acute calamity of the novel when Wolsey’s ghost ceases to talk, leaving him “without company, without advice”. He can but turn to those he in turn has sponsored. Rafe Sadler, Thomas Wriothesley: “he has trained them, encouraged them, written them as versions of himself”. Watchfully, appreciatively, resisting hindsight, the novel asks what they have learned.

“There is nothing against the recreation of the dead,” Cromwell says, “as long as they are plausible.” He has just employed Holbein to paint the past kings of England, inventing their unknown faces. It’s as if he is glancing towards Mantel, signalling permission. Where evidence survives, she uses it; where there is silence, she offers deeply informed guesses about the world as it looked to him. It’s characteristically bracing of her to consider the horror of finding that one’s life is wrongly told: Cromwell has forced on many victims an “estrangement of self” and suffers in his turn from contortions of evidence, wilful misreadings. Of the book’s many mirrors, this is the most disturbing: the glass in which the truth of your life is stolen away and reconfigured. Mantel’s project is to offer a clearer reflection, a more plausible hypothesis, a more telling illumination.

She is still exuberantly rethinking what novels can do. Not since Bleak House has the present tense performed such magic. The narrative voice rides at times like a spirit or angel on thermals of vitality, catching the turning seasons, the rhythms of work and dreams, cities and kitchens and heartbeats. Mantel did not have much to learn about scene-setting or dramatic timing, but her involvement in the staging of Wolf Hall, and the experience of watching the television adaptation, may have contributed to an ever-finer honing of dialogue. In a room at the Tower, in the time it takes to burn two candles, a prisoner’s silence mounts towards confession. On a thundery midsummer night, talking quietly in a garden tower at Canonbury, eating strawberries while the moon comes up, two men arrange the future “a hair’s-breadth at a time”.

Endings, insists Cromwell, are opportunities. What begins now is the rereading. For this is a masterpiece that will keep yielding its riches, changing as its readers change, going forward with us into the future.

• The Mirror & the Light is published by 4th Estate (RRP £25). To order a copy go to guardianbookshop.com. Free UK p&p over £15.