Cornelius: “Do you see the trick of it, John?”

John: “I think so.”

Cornelius: “No fear.”

And, finally, once the pair cast off in a leaky boat on the dark waters of Clew Bay, an island — not his own, but familiar to John — where reside the remnants of a cult presided over by a man with “the look of an enormous forest hog” who goes by the name of Sweet Joe.

John: “I’ve been here before.”

Cornelius: “We’ve all been here before, John.”

The next 76 pages read like a nightmare from which you find yourself wishing John would just wake up — but you can’t put the book down, so you soldier on together.

If you’re looking for a good informational read about John Lennon, then my guess is you’ll do better elsewhere. While it will be obvious to any hard-core fan (guilty!) that Barry knows as much about Lennon’s life as most of his biographers, that’s not what this book is about — it’s far more ambitious. That’s not to say that “Beatlebone” could have been written about just any rock star. Nor for that matter could it have been written by just any writer. Only a literary beast, a daredevil wholly convinced he was put on this planet to write, would ever or should ever attempt to cast a person as iconic as John Lennon as a character in a tale of his own invention. Kevin Barry, whose previous novel was the dystopian “City of Bohane,” is that beast.

The fictional Lennon in these pages is fashioned on a skeleton of what we know about the public Beatle and what we think we know about the very private man. When you read John’s words you can hear the nasal scouse accent we remember from “A Hard Day’s Night” propelling his banter with Cornelius and the low mumble of “Revolution 9” in the constant comments under his breath. But this story takes place in 1978, a period in which the real John Lennon was all but invisible to the world outside of the Dakota, and therefore the muscle and blood of the character are largely conjecture — purely gossip in the hands of the average hack, but Barry is no hack. The John we meet on a journey in the west of Ireland in search of his creative (if not his former) self is fully formed, fleshed out with our own hopes and dreams and, one would assume, those of the author, because real writers can only write about themselves.

And real writer or not, the character of Cornelius O’Grady could only have been created by an Irishman.

Books like this come along once in a generation, books by writers with real chops, who haven’t yet been discouraged from taking real chances and blurring the lines between disciplines. Barry employs every tool in his formidable toolbox — ­razor-sharp prose, powerful poetics and a dramatist’s approach to dialogue unencumbered by punctuation. The continuing conversation between John and Cornelius is the narrative engine of the tale of the Irish odyssey in 1978, but other voices are employed, each with a specific function: self-conscious prose when John’s alone and without the cover of Cornelius’s glib counterpoint; flowing, haunting free verse when he succumbs to haunting memories of his youth in Liverpool and his ghostly imaginings of the courtship of his mother and father.