What can I say here that won't end up as a huge spoiler for those who haven't yet finished reading the series? I think I'll stick to the character bio you can find in the Fifty Shades of Grey Wiki (click at your own risk, beware of spoilers!):
"Christian Grey is the male protagonist of the trilogy that serves as Anastasia Steele's primary love interest with whom he discovers real love. Young, handsome, intelligent, business-savvy, and charming, he at first glance appears to be a suave but private business mogul with an irresistible allure. Upon further acquaintance with him, and later on, a relationship, Anastasia finds out that there is a darker side to "control freak" Christian, quoted as being "fifty shades of f*cked up." (Hence the title of the first book in the Fifty Shades Trilogy)."
(In reading order)
