Harley Quinn Reading Order
Harley Quinn is a rarity in the Comic Book World because she was created on TV by Paul Dini and Bruce Timm in Batman: The Animated Series, in 1992. She became a recurring character on the show and, because of her popularity, she made the transition to paper, joining the Batman comic book canon seven years later.
Here was her story at the beginning, as told in the Mad Love comics: When she was only seven years old, Harleen Quinzel witnessed her father being beaten up by thugs, and then arrested by the police. That night she ran away to the safest place she could think of: Coney Island amusement park. But there, pursued into the Funhouse by the men who brutalized her father, she beheld unimaginable horrors. Years later, Harleen has put her past behind her and used her intelligence and ambition to escape her childhood of poverty with a career in psychiatry. Assigned to her first position at Arkham Hospital, she will discover, deep in the asylum, something dangerous and alluring, something quite unlike anything else she has ever known before: The Joker.
She became Harley Quinn and, after having been injected with a special formula by Poison Ivy, she got new abilities, such as immunity to toxins and enhanced strength and agility. She left Joker behind and became a solo criminal. It was not a hit at first, but Harley came back a few years after the end of her first solo series to team up with Catwoman and Poison Ivy (forming the Gotham City Sirens).
Harley was a criminal, then an anti-heroine. Her backstory was refined, as her relationship with Poison Ivy. She became quite popular on paper (especially during the 2010s), and later on the big screen too.