Frankenstein, renowned Gothic horror novel and forerunner of the science fiction genre as we know it, is perfectly capable of giving almost anybody a fright. But it probably startled a London man called Sammy Jay more than most when he stumbled upon a very special copy of it last year.

He was digging through the long-disused personal library of his grandfather, Lord Jay, the late economist and Labour politician, with the aim of gathering political papers for Oxford’s Bodleian Library archives when he found the rare volume.

The Telegraph reports Jay’s copy, with “To Lord Byron, from the author” inscribed  by Mary Shelley herself on an inside page, was recently purchased by a UK collector at auction for an undisclosed sum.

The asking price was a staggering £350,000.

There are several reasons for the gruesomely large figure, one being that a mere 500 copies were initially printed and of those no more than 25 are thought to have been kept by Shelley to give to her friends.

She published the book anonymously when she was just nineteen years old.

Before Jay’s discovery, the only other known signed copy in existence was one kept at the Morgan Library & Museum in New York.

But Jay’s, of course, wasn’t just another autographed print. It had been gifted to Byron of all people — the very man who, along with Mary’s future husband Percy Bysshe Shelley, infamously instigated a scary story-writing competition that lead directly to the novel’s creation.

Peter Harrington, the rare book dealers responsible for the recent auction of Byron’s copy, have happily announced that this print will stay in the UK, and that the new owner intends to make the book available for public viewings and exhibitions there.

Has the price tag struck more terror in your heart than Frankenstein’s monster? Check out the Telegraph’s new feature, Printing history: the most valuable rare books in existence, to gain some perspective.

British books on that list include first editions of Wuthering Heights, On the Origin of Species, the King James Bible, and the collected works of Shakespeare.