If you’re going to attempt to rewrite a classic, you darn well better have a fresh perspective and not a hacky, overwrought “surprise” ending tacked on in the final two pages.

Somebody really should have told that to Peter Ackroyd before he tried sparking new life into “Frankenstein,” only to churn out a limp mockery of Mary Shelley’s masterpiece.

Ackroyd’s writing is actually quite engaging, and the pacing is crisp and fluid enough to keep things interesting, but he never brings anything fresh to the table. Told from the perspective of the eponymous doctor, Ackroyd imagines a friendship between the young Frankenstein and his Oxford schoolmate, Percy Bysshe Shelley.

Frankenstein is captivated by Shelley’s joie de vivre. The self-important Shelley feeds off the attention Victor gives him. Both are fascinated by the concept of a new era dawning. For Shelley, it is an era of poetry, revolution and godlessness. For Frankenstein, it’s an era of medical miracles and the triumph over death, a concept that’s much more attractive as a poetic precept than experimenting on purloined corpses.

Frankenstein begins his experiments and eventually creates the monster that will come to torment him and force him to reassess his philosophy of life and death. Ackroyd never manages to evoke the horror and ethical conflict that Mary Wollstonecraft Shelley wrought, and his casebook is a stale retelling that pales in comparison to the original.

Theoretically, a first-person narrative of Victor Frankenstein seems promising, but Ackroyd turns the doctor into a bore, and makes him surprisingly daft.

Ackroyd even manages to throw a wet blanket over one of the most fascinating literary soirees ever, the 1816 Villa Diodati retreat where the Shelleys, Lord Byron and John Polidori ate, drank and came up with stories designed to scare the pants off each other. That getaway spawned both Shelley’s “Frankenstein” and Polidori’s “The Vampyre,” which helped influence Bram Stoker’s “Dracula.”

In Ackroyd’s version, Frankenstein joins those esteemed guests and Mary’s story is simply a telling of somewhat true events. It’s an insulting and condescending portrayal of Mary, who was not only a trailblazer as a female author (“Frankenstein: or The Modern Prometheus” was published under her own name when she was just 21), but whose work even at such a tender age is far superior to Ackroyd’s weak retelling.

In fact, the feeling that builds throughout the book isn’t a sense of dread, anticipation, or suspense, but simply a curiosity over what Ackroyd is trying to achieve with such a watered-down version of a story that has been told, retold, and parodied to death.

Ackroyd pulls a weak “surprise ending” in the final two pages, but nothing in the book builds to that premise. It’s a sloppy effort that does nothing but make you want to reread Mary Shelley’s original.

Dan Murphy is a freelance Buffalo writer.

The Casebook of Victor Frankenstein By Peter Ackroyd Nan A. Talese/Doubleday 372 pages, $26.95