Shannon's mother says she was a storyteller from birth, jabbering endlessly in nonsensical baby-talk. Once she could speak, she made up stories and bribed younger siblings to perform them in mini-plays until, thankfully, an elementary school teacher introduced her to the wonder of written fiction. At age 10, she began to write books, mostly fantasy stories where she was the heroine. 

She continued to write secretly for years while pursuing acting in television, stage, and improv comedy and a bachelor's degree in English from the University of Utah. Shannon was finally forced out of the writers' closet when she received her Masters in Creative Writing from the University of Montana.

A few years and many rejections later, she published her first book, The Goose Girl, an ALA Teens' Top Ten and Josette Frank Award winner. Enna Burning, River Secrets, and Forest Born continue the award-winning Books of Bayern series. Princess Academy won a prestigious Newbery Honor award and is followed by bestsellers Princess Academy: Palace of Stone and Princess Academy: The Forgotten Sisters. Book of a Thousand Days received a Cybils award and was featured on many best of the year lists. With director Jerusha Hess, Shannon co-wrote a screenplay based on her first book for adults, Austenland. Shot in England, the film was a selection at the 2013 Sundance Film Festival and was released theatrically by Sony Pictures Classics. She penned a sequel, Midnight in Austenland, as well as a third novel for adults, The Actor and the Housewife, which was the City Weekly readers' choice winner for best novel of the year. She and her husband Dean Hale co-wrote the graphic novels Rapunzel's Revenge, an Al Roker's Book Club for Kids selection and Eisner nominee, and its sequel, Utah Book Award winner Calamity Jack, both illustrated by Nathan Hale. With illustrator LeUyen Pham, they created the Princess in Black series of early chapter books.

In addition to her own creations, Shannon has written a number of books about characters created by others, such as her Ever After High series, supported by Mattel's animated series and doll line; with her husband Dean, two books about Marvel's Squirrel Girl; and the fourth book in the Spirit Animals series. She makes her home near Salt Lake City, Utah, USA, with her super-human husband, their four children, and their two cats, Misty Knight and Mike Hat.