EL James' erotic tale about a billionaire's quest to sexually dominate a naive literature student has been nominated for Britain's National Book Award in the category of popular fiction.

The awards celebrate books that have won wide popular appeal, critical acclaim and commercial success and are selected by panel of 50 book experts, including booksellers and trade journalists.

The nomination of Fifty Shades, which has sold more than 3 million copies in Australia, comes as another surprisingly sexy tale makes waves in Britain – this time in the newly coined genre of "granny-lit".

A tale of 60-somethings romance, Thursdays in the Park, by British grandmother Hilary Boyd, has become a word-of-mouth e-book hit, with the digital edition quietly outselling thriller writer Ken Follett and Fifty Shades Of Grey.

The novel features a sexually frustrated pensioner who starts a romance with the man of her dreams while babysitting her grandchildren.

Just as the blockbuster sales for Fifty Shades sparked a rush of copycat women's erotica, Thursdays in the Park has been hailed as a pioneer of a new category of contemporary women's fiction devoted to late-flowering love.

The book could be a contender for next year's popular book category. Meanwhile, E.L James' novel is up against Me Before You, by JoJo Moyes, Victoria Hislop's The Thread, 1356, by Bernard Cornwell, Cit-adel, by Kate Mosse, and The Rose Petal Beach by Dorothy Koomson.

For The Casual Vacancy, J.K Rowling's first foray into adult fiction, the author of the Harry Potter series has been nominated as UK Author of the Year, alongside this year's Booker prize-winner Hilary Mantel (for Bring Up the Bodies), as well as Zadie Smith (for NW) and Jeanette Winterson (for Why Be Happy When You Could Be Normal).

Other notable nominees include rocker Peter Townshend and comedian David Walliams for their respective autobiographies, Who I am and Camp David.

In the category of International Author of the Year, Patrick deWitt has been shortlisted for The Sisters Brothers. Also nominated are Daniel Kahneman for Thinking, Fast and Slow and Herman Koch for The Dinner.

The winners are chosen by votes from the National Book Awards Academy, comprising 750 industry experts. Previous winners of the popular fiction award include Dawn French for A Tiny Bit Marvellous, David Nicholls for One Day and Sebastian Faulks for Devil May Care.