Many different authors have written books featuring the Olsen twins. Some examples include:
* Nancy Springer wrote many of the early "Mary-Kate and Ashley" books, like the "You're Invited" series and "Mary-Kate and Ashley: The Mystery of the Hidden Treasure."
* Wendy Lichtman also wrote several "Mary-Kate and Ashley" books, including the "Passport to Adventure" series.
The publishing house that produced the books, Random House, typically hired a team of writers who were familiar with the target audience.