Spirit Hunters: The Island of Monsters (2018).It was held online May 1 and 2, 2020, focusing on children's literature with 43,000 viewers attending. In 2020, Oh, Christina Soontornvat and Melanie Conklin created the Everywhere Book Fest, due to COVID-19 cancelling in-person book festivals. The story was influenced by Korean Shamanism, and was published in 2017.

The first scene she wrote for the book was influenced by the hospital room and, according to Oh, based on 'that feeling of depression and horror and sadness and fear that I was feeling and that I know my kid was feeling.' The book follows a young child, Harper, and her family as they move into a seemingly haunted house. Oh's book, Spirit Hunters, was started after her daughter was hospitalized due to depression.

In 2016, Oh was a judge for the National Book Awards in the young people’s literature category. As of 2020, she is currently the president of WNDB. For her work, Oh was named one of Publishers Weekly's Notable People in 2014. The organization We Need Diverse Books (WNDB) was incorporated in the summer of 2014. The campaign, launched on May 1, 2014, gained 106 million Twitter impressions in the first 24 hours. In response, Ellen Oh and others in the industry created a Twitter campaign under the hashtag #WeNeedDiverseBooks. In 2014, BookCon announced an all-white line-up for the event and hosted a children's book author panel consisting of all-white, all-male participants. The series, known both as the Prophecy trilogy and the Dragon King Chronicles, draws from Korean folklore. Prophecy, the first book in Oh's young adult fantasy series, was published in January 2013. She began to write seriously after she had children, prompted by her struggle to find books that included representations for her kids. She attended New York University and Georgetown University, graduating with a legal degree. She is the award winning author of young adult and middle grade novels including the Prophecy trilogy, also known as the Dragon King Chronicles, a series of fantasy, young adult novels based on Korean folklore. Ellen Oh (née Ha) is a Korean-American author, and founding member and CEO of the non-profit We Need Diverse Books.

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