Compiled from news reports

The "Fifty Shades" erotic trilogy is expected to hit the 20 million-sales mark in the U.S. this week, making it one of the fastest-selling book series in recent memory.

After quickly becoming an overnight literary sensation among women in Britain, the trilogy, starting with "Fifty Shades of Grey," had sold 19.4 million copies in both print and e-book form in the U.S. since its publication in March.

In a joint statement today, Universal and Focus called the word-of-mouth sensation a “special story,” an explicit tale about billionaire Christian Grey and college student Anastasia Steele.

The first in a trilogy of erotic novels about the 21-year-old recent college graduate and her lurid relationship with the billionaire in his late 20s, the modern-day Mills and Boon novel centers on Grey, whose damaged sexual upbringing prompts him to engage in relationships with women who will agree to become his submissive.

Around the world, the "Fifty Shades" books have sold a total of 31 million copies in English-language markets.

The book, by British writer EL James, was first published by a small Australian firm that printed only a small run and released it as an e-book.

The erotic novel put grey ties at the top of many wives shopping lists, in the hopes their husbands would emulate Grey's “brooding, masterful and intimidating” character, with many admitting reading the book made them crave sex with their partners.