When an author you love writes a book you really don’t, it can feel like an act of personal betrayal. Michael Chabon’s best novels – The Amazing Adventures of Kavalier & Clay, Wonder Boys and The Yiddish Policemen’s Union, as well as his underrated debut, The Mysteries of Pittsburgh, are among the most luminous and finely crafted books of recent decades. He’s a writer who leaps nervelessly across genres and themes: from magic realism to detective fiction, from comic-book heroes to campus Künstlerroman. Always, though, there was the lightness of touch, the graceful precision of the prose, the sense that here was a writer whose heart was several sizes bigger than any of his peers.

In 2012, I did an event with Chabon at the Cheltenham literature festival to celebrate the launch of Telegraph Avenue, his eighth novel. I’d finished it on the train up and it stank. I could scarcely look him in the eyes. It was sententious and low concept, as if someone had leached the joy from his world and the spark from his imagination. All the things I’d loved about Chabon’s early work – the surreal Bruno Schulz flourishes, the picturesquely neurotic characters, that radiant voice – were suddenly loathsome. Moonglow, his latest, landed on my doorstep with an ominous thud.

The truths the book tells are deeper than history, more enduring than mere facts

Moonglow holds itself out to the reader as the memoir of Chabon’s grandfather, narrated to the author on the old man’s deathbed. Like a peppy, Californian Knausgaard, Chabon is exploring the fertile hinterland between fact and fiction, feeding what David Shields calls “reality hunger”. The first-person narrator of the book is a writer named Mike Chabon whose life, at least from the little we’re allowed to see of it, adheres closely to that of the real-life Chabon. There are footnotes, an advertisement clipped from a magazine, regular lists of physical objects that insist upon their place in the real world: all the appurtenances of the memoir genre.

The grandfather, an unnamed engineer, has lived a vivid and rambunctious life and now, dying of bone cancer and loose tongued from painkillers, he relates his history to Mike with the garrulousness of one who knows his time is short. The novel is structured haphazardly as far as chronology goes, leaping from the grandfather’s wartime exploits to his marriage to a period in jail. These jumps in time could be discombobulating, but we recognise a deeper logic at work in their construction – memory, hunting in the dark for truths and affinities within the seeming randomness of a life. “After I’m gone, write it down,” the grandfather tells Mike at one point. “Explain everything. Make it mean something. Use a lot of those fancy metaphors of yours. Put the whole thing in proper chronological order, not like this mishmash I’m making you.” The mishmash is important, though. It’s all part of the book’s project, its reality effect.

The grandfather’s war is beautifully rendered. Just as Kavalier & Clay was both about the writing of superhero comics and a kind of superhero comic itself (albeit in prose form), here we have a rollicking story within a story full of doodlebugs and desperate raids that never descends into pastiche. The scenes of the rocket-obsessed grandfather racing through ruined, defeated Germany in search of Wernher von Braun are compelling. The book acknowledges its debt to that other great novel of ballistics, Thomas Pynchon’s Gravity’s Rainbow, even having Mike go to the library to reread the novel at one point. While Gravity’s Rainbow was as sharp edged and thrusting as a futurist painting, Moonglow has a softer focus. The grandfather can’t forget what he witnesses at the liberation of KZ Dora, the concentration camp at Nordhausen where inmates were made to work on the V2. When the family gather round the television to watch the moon landing 25 years later, the grandfather, despite his rocket obsession, leaves the room. He recognises the cost of progress, the stain that spread from von Braun to the whole space programme.

There is a crucial scene towards the end of the novel that seems to me to illustrate Chabon’s project in Moonglow. Mike and his mother are leafing through an old photograph album from which four photos – of the narrator’s grandmother – are missing. The photographs that are present are spooled through so swiftly that we almost don’t see them; then, over several pages, Mike and his mother work together to reconstruct the missing photos. This work of the imagination, the filling in of blanks – this is what novels can do. Moonglow is a book that seeks to challenge the primacy of facts, the reality fetishism that sees every film plastered with “based on a true story”. “Everything you’ve been telling me is true, though, right?” Mike asks his grandfather at one point. “Well, it’s all the way I remember it happening,” the grandfather replies. “Beyond that, I make no guarantees.” The truths the book tells are deeper than history, more enduring than mere facts.

Moonglow is full of the kind of prose that made me love Chabon in the first place. A flying bomb lies “jammed into a frozen pond like a cigar butt into the sand of an ashtray”; the grandfather’s schizophrenic wife sets a tree alight and “the hickory stood rigged in sails of fire”. The central relationship – between the grandparents – is depicted delicately and movingly, the war ever-present in the form of the damaged, dignified wife.

This is a novel that, despite its chronological lurches, feels entirely sure footed, propulsive, the work of a master at his very best. The brilliance of Moonglow stands as a strident defence of the form itself, a bravura demonstration of the endless mutability and versatility of the novel. By the time I’d finished, Telegraph Avenue felt like nothing more than a brief bad dream.

• Moonglow by Michael Chabon is published by 4th Estate (£18.99). To order a copy for £15 go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99