J K Rowling
J K Rowling poses with a copy of her book Harry Potter And The Half-Blood PrinceReuters

A magical 29% rise in Harry Potter sales helped publisher Bloomsbury achieve a 1.5% increase in revenue to £111.1m (€154.6m, $171.63m) in the year to 28 February 2015.

The company published a new edition of the JK Rowling books with covers by illustrator Jonny Duddle. Previously, the books series has been published with several covers, including a celebratory edition, an adult edition and a signature edition.

Bloomsbury decided to publish the Harry Potter series after the daughter of the company's chief executive said she loved the books.

The success of the new cover edition balanced out the disappointing adult book sales. Adult book sales went down by 10.4% and profit in that section plummeted by 41.17% due to high investment costs.

"We continue to develop our strategy of global publishing through the acquisition of global rights wherever possible," Bloomsbury stated regarding the adult book sales.

The children and education section of the company was carried by other shooters such as John Green's popular young adult book Paper Towns.

A film based on Green's novel will come out in July this year and will star British model Cara Delevingne and actor Nat Wolff and is expected to be a great box office success.

Chief executive and founder Nigel Newton said it had been a good year for Bloomsbury and he is happy with the results.

"The year was characterised by the consistent development of the strategic aims of the business – in short, digital investment, a greater proportion of business generated from academic and professional publishing ... and a focus on marketing to discrete communities of interest," Newton said.

He added that Bloomsbury will push to increase the quantity of sales and focus on the company's academic and professional division.

"We continue to reduce costs in the business through volume-based tender processes," Newton said. "Having reviewed mono and colour print, prepress, image licensing and conversion costs over the past two years we will be assessing freight costs and editorial services in the forthcoming year."

The publisher said it will pay a total dividend of 6.02p, up 4.8% from last year.