A erotic romance novel about a recent college graduate who enters into a sexual relationship with a billionaire control freak. They have a BDSM relationship, he hits her/ties her down while they have sex, is controlling and domineering.
The book was written by a woman and self published on Amazon.
As of 2017, the trilogy had sold 150 million copies globally. For comparison, Harry Potter has sold 500 million copies worldwide for a seven book series.
The original in the series was the best selling book of the 2010-2019 decade in the US, selling 15 million copies, large majority to women. That comes out to 1 sale of the book for every 11 women in America. The trilogy holds the #1, #2, and #3 positions in sales for the same decade.