
When literature student Anastasia Steele goes to interview young entrepreneur Christian Grey, she encounters a man who is beautiful, brilliant, and intimidating. The unworldly, innocent Ana is startled to realize she wants this man and, despite his enigmatic reserve, finds she is desperate to get close to him. Unable to resist Ana’s quiet beauty, wit, and independent spirit, Grey admits he wants her, too—but on his own terms. Shocked yet thrilled by Grey’s singular erotic tastes, Ana hesitates. For all the trappings of success—his multinational businesses, his vast wealth, his loving family—Grey is a man tormented by demons and consumed by the need to control. When the couple embarks on a daring, passionately physical affair, Ana discovers Christian Grey’s secrets and explores her own dark desires. Erotic, amusing, and deeply moving, the Fifty Shades Trilogy is a tale that will obsess you, possess you, and stay with you forever. This book is intended for mature audiences.
Just because an established Hollywood director was a fan of the first Alien movie does make his script for Alien's sequel "fan fiction".
Cameron had already written and directed The Terminator when the owners of the Alien franchise chose his script for the sequel.
(Fifty Shades of Grey in contrast really did originate as fan fiction.)
You can read "Moby Dick" as a story about a fish, and you can read "50 shades of grey" as a treatise on existentialism and the human spirit- it's all up to you!
A book nerd could come up with a much longer list, but I know there's a ton more illegal unlicensed! Harry Potter fan fic.