As Victor Frankenstein begins conducting anatomical experiments to reanimate the dead, he at first uses corpses supplied by the coroner. But these specimens prove imperfect for Victor’s purposes. Moving his makeshift laboratory to a deserted pottery factory in Limehouse, he makes contact with the Doomsday men–the resurrectionists–whose grisly methods put Frankenstein in great danger as he works feverishly to bring life to the terrifying creature that will bear his name for eternity

Facts have little place in Peter Ackroyd’s historical fiction, which, broadly speaking, falls into two categories: novels such as Chatterton, Hawksmoor and The House of Doctor Dee, in which parallel narratives in the past and present subvert accepted historical truth; and novels such as Milton in America and Dan Leno and the Limehouse Golem, which present full-scale alternative realities.

Ackroyd’s latest novel belongs to the second category, but with an added twist. Two of Gothic fiction’s most durable characters, Victor Frankenstein and his Creature, not only inhabit the same world as their creator, Mary Shelley, but have a decisive influence on it.As is well known, Mary dreamt up the plot of Frankenstein after a night of ghost stories at the Villa Diodati, where she and Shelley were staying with Byron. In Ackroyd’s version, there is an additional guest: Frankenstein himself.

The Swiss doctor befriends Shelley at Oxford, where he is pursuing his scientific studies. Indeed, it is the poet who puts in his mind the idea that “the animal electricity of Signor Galvani” might be applied to human beings.

Frankenstein in turn aims to create “a sentient human being unencumbered by class or society or faith…Bysshe’s dream child”. Ackroyd supplies a vivid practical background involving anatomists and “sack ’em up men” (resurrectionists), although he fudges the details of the procedure: “This I managed after much weary labour and experiment by means of a certain operation in the cerebellum,” declares Frankenstein.

The Creature, born of “the most beautiful corpse I had ever seen”, immediately disappoints. Not only does his beauty vanish but he reveals his bestial nature – his first impulse is to masturbate.

He holds his creator responsible for both his suffering and his misdeeds, informing him: “You are the guilty agent of my misfortune. I did not seek for life, nor did I make myself,” words that echo Milton’s Adam, whom Byron quotes later in the novel.

The Creature embarks on a course of destruction, targeting Shelley’s first wife, Harriet Westbrook, who, in Ackroyd’s version, is not the educated daughter of a West End coffee-house owner but an impoverished East End girl whom Shelley rescues from a life of drudgery.

Instead of drowning herself in the Serpentine after he deserted her for Mary, she is here murdered by the Creature before Shelley even meets Mary.

Further mayhem ensues before the Creature’s appetite for revenge is glutted, and it would be unfair to reveal the details of what is a fiendishly clever literary conceit.

As always in Ackroyd’s novels, however fanciful the foreground, the background is meticulously researched, with fascinating incidental detail, such as the practice prevalent in Limehouse of burying a corpse under the floorboards to save the expense of a funeral.

There is, nevertheless, a sense that Ackroyd is not so much recreating the past as itemising it.

Ackroyd’s most deeply felt passage is the Creature’s account of his encounter with a labourer and his daughter through whom he discovers the power of poetry. The whole novel is steeped in literature: verse is frequently quoted – and even misattributed (the quatrain beginning “Youth of tumultuous soul, and haggard eye!” which Frankenstein sees credited to Shelley in the Monthly Magazine is actually by Coleridge).

Throughout the book, Ackroyd plays games with literary history: for example, Byron’s personal physician, the Roman Catholic Polidori, is here reinvented as a Jew in order to tell Frankenstein about the ancient legend of the Golem, of which Mary Shelley’s novel is itself a variant.

The Casebook of Victor Frankenstein┬áis a brilliant jeu d’esprit. It is hard to detect any serious purpose behind it unless it is the one expressed in the Creature’s remark to Frankenstein: “There is no substance…without a shadow.”

The novel is constructed on a complex set of dualities: Shelley’s and Frankenstein’s Promethean dreams; Harriet giving birth as Frankenstein gives life to the Creature; Shelley’s vision of a doppelganger while at Eton; Frankenstein and the Creature as two aspects of the same self.

Above all, it stands as a tribute to the power of the human imagination: Shelley’s poetic imagination; Frankenstein’s scientific imagination; and Ackroyd’s literary imagination that unites the two.