As if dominating worldwide book sales wasn’t enough, ‘Fifty Shades of Grey’ will now be issuing an accompanying classical music album to the trilogy.

reports that ‘Fifty Shades of Grey’ author E.L. James has selected fifteen classical tunes to be part of ‘Fifty Shades of Grey - The Classical Album.’

The trilogy, dubbed to be “mommy porn,” has trumped other literary greats including the Harry Potter series and The Da Vinci Code as becoming the fasting selling paperback worldwide. In Ireland alone, the books have sold over 12 million copies.

Author E.L. James said “I am thrilled that the classical pieces that inspired me while I wrote the Fifty Shades trilogy are being brought together in one collection for all lovers of the books to enjoy.”

Billboard also reports that EMI Classics, the label for the upcoming compilation album, credits the book trilogy with a recent boost in classical music sales. In particular, the 16th century classical song ‘Spem in Alium’ rose on the charts after being referenced in the books.

Prior to its mention in the book, the Peter Phillips & the Tallis Scholars' version of the song had been available online since 2006, though never receiving more than a few downloads a week. In May, its popularity skyrocketed with about 1,000 downloads weekly. Then, in June, it debuted on Billboard's weekly Classical Digital Songs at number 19 and has since peaked on number 5 on the chart.

‘Fifty Shades of Grey - The Classical Album’ will be available for purchase digitally on August 21 and in stores September 18.