She reigns supreme in the world of paper, with The Cuckoo's Calling topping hardback sales and The Casual Vacancy sitting at the top of the paperback bestseller charts, but there's no space for JK Rowling on the inaugural ebook bestseller list. Instead the top 50 UK ebook chart – compiled by the Bookseller from publishers' reports – is filled with erotic fiction, with the latest in Sylvia Day's raunchy Crossfire series installed at No 1.

"The first chart is based on data for June so that's obviously before JK was outed," Philip Jones, editor of the Bookseller said. With Amazon keeping ebook sales close to its chest, he explained, no official figures exist for electronic sales, so the Bookseller has gathered information from UK publishers to give an indication of sales in an increasingly important part of the maket.

"Initially, we've compiled data from six of the biggest publishers in the UK, which together represent 51% of the print book market, and 81% of print fiction, and we hope to add more publishers very soon."

Dan Brown reaches number two in June's ebook top 50, with Inferno, the fourth Robert Langdon novel, and Gillian Flynn's Gone Girl charts at number three. Erotica and crime feature strongly, there's a good peppering of literary fiction, but non-fiction is sparse and children's books failed to chart at all.

The ebook top 50 universe reveals that digital versions sold 784,000 copies, compared to 1.3m print copies, giving ebooks a 37% market share; this compares to 25% ebook share for the entire UK book market.

Twelve books from the ebook top 50 sold more in ebook form than in print, including Sylvia Day's Entwined with You (55%), Lee Child's Jack Reacher thrillers Killing Floor (65%) and Tripwire (59%), Gillian Flynn's backlist thrillers Dark Places (79%) and Sharp Objects (80%), and Julie Kenner's erotic tales Release Me (86%) and Claim Me (85%).

There are only two non-fiction titles on the list, Miranda Hart's Is It Just Me? And Dr Michael Mosley and Mimi Spencer's The Fast Diet, compared to seven in the comparable printed book ranking, which features the likes of Karl Pilkington's The Further Adventures of An Idiot Abroad, and Rick Stein's India. No children's titles make the cut, while in the print world David Walliams's Gangsta Granny is in the top 50.

Literary fiction makes a good showing alongside the erotica and crime. Khaled Hosseini's And the Mountains Echoed is in at number four, Hilary Mantel's Bring Up the Bodies at 19, and Wolf Hall at 48, Kate Atkinson's Life after Life charts at number 23, and Sweet Tooth by Ian McEwan is at number 40.

Dawn French's Oh Dear Silvia is the highest-selling printed book of the month which doesn't appear in the ebook chart; the paperback is selling to the tune of 43,445 a week, to put it at number five in the print book bestseller list, but fails to make the 5,262 copies minimum ebook sale required to earn a place in the top 50 ebooks.

While this isn't a definitive list, Jones is confident that the new chart offers a fair reflection of the ebook market.

"We hope this is a useful measure of ebook sales at a time when the industry and readers are moving fast in their digital adoption. That said, with ebook sales of 200k, it's a safe bet that Sylvia Day can count herself an ebook bestseller, as well a print-book bestseller."

• If you'd like to receive the ebook chart in full, email ebookcharts@bookseller.co.uk with subject line "Free chart"