Elizabeth Hand described the book as "exquisite ... an exceptionally frightening novel whose nightmare power derives from its chilling, almost clinical evocation of an historical reality with which we are all familiar, the London Blitz... a cliffhanger narrative of dual identities, betrayals, and shifting realities, as two versions of the twins' histories—and England's, and the world's—are woven together, like strands of DNA, to form a terrifying narrative. Priest has used doubles before to great effect, in his award-winning novel "The Prestige"; but "The Separation" trumps even that tale. Its chapters linger in the mind like scenes from a Hitchcock film, impossible to shake off; like Hitchcock's work, "The Separation" begs for repeated readings to appreciate the cold brilliance and execution of its intricate plot fully. A masterly novel that deserves to become a classic."