THEY bear eerily similar covers: stiletto heels, satin sheets, lips and other hints of bare flesh, a locket and antiquarian key photographed against backgrounds of burnished blacks, steel greys and metallic blues.
Their blurbs hint of secrets, seductions, thrilling love affairs that push the characters to ''their limits'', tormented lovers and slap-and-tickle foreplay. Publishers pitch the look-alikes ''for fans'' of the Fifty Shades trilogy hungry for more of the same, and readers are gobbling them up.
With global sales of 40 million, the success of the Fifty Shades of Grey trilogy has encouraged a crop of imitators.
The Australian bookstore chain, Dymocks, estimates 40 titles in this genre have been published or republished in the wake of Fifty Shades's March release, warranting a new category called steamy fiction.
''While the best of the 'copycat' books for Dymocks have only sold a fraction of Fifty Shades, these are nevertheless strong sellers for us that have, almost without exception, entered our top 10 bestseller lists on release and we are buying up everything that comes our way while our customers are showing such a strong appetite for it,'' said a Dymocks buyer, Sophie Higgins.
''There is no doubt that this will be an ongoing growth category for Dymocks. Romance has always had a loyal and wide readership, but the extra-naughty modern nature of these books and all the publicity has really taken it to a wider and perhaps a slightly younger audience.''
Bandwagon publishing is not new, Ms Higgins said. Twilight triggered growth in the young adult and paranormal romance categories, Scandinavian crime grew in profile after Stieg Larsson's The Girl with the Dragon Tattoo, and The Hunger Games tripped the trend to dystopian adult fiction.
The first to follow in Fifty Shades's mighty sales wake were Destined to Play from HarperCollins, The Secret Lives of Emma from Random House and Bared to You from Penguin, all of which were published in July.
Nikki Gemmell's 2003 literary novel The Bride Stripped Bare has recently received a Fifty Shades of Grey makeover and new editions carry a metallic grey livery designed to appeal to the trilogy's audience.
Among the parodies and mashups is Fifty Shames of Earl Grey and Fifty Shades of Mr Darcy, the latter featuring a cover of riding boots and crop.
The adult fiction publishing house Clandestine Classics is reworking classics such as Jane Eyre and Pride and Prejudice to include explicit sex scenes.
While the covers evoke the style of Fifty Shades of Grey, copyright infringement does not come into play because they are not copies of the original, said Kevin Lynch, a partner at Johnson Winter & Slattery.
''The lookalikes are unlikely to mislead a fan of Fifty Shades, given the books have different authors,'' he said. ''They are imitations, but there is no law against sincere flattery.''