The Accidental Mistress by Portia Da Costa

Seduced by a billionaire. After being mistaken for a high-class call girl when they first met, Lizzie now enjoys a fiery relationship with John, her gorgeous and incredibly rich older man. Devoted, romantic and devilishly kinky, John knows exactly how to satisfy her every need. But John has a dark side - and a past he won't talk about. He might welcome Lizzie in his bed - and out of it - but will she ever be anything more than a rich man's mistress?