The Fault in Our Stars is dedicated to Esther Earl. However, it is clear from Green's Author's Note that he does not wish the public to read the book as if it were based directly on Esther's life. Green has written on his Tumblr, "I don’t want people conflating Esther with Hazel (they’re very different), and it’s extremely important to me that I not claim to be telling Esther’s story." Green drew inspiration for Hazel's story from his experiences and conversations with Esther as well as experiences working as a chaplain at a children's hospital and from relationships with his wife and son. Because it is clear that Green's friendship with Esther greatly affected the writing of the book, it is important to understand their relationship and her life. Furthermore, her life, and the response of her parents, Green, and Nerdfighteria after her death is an inspiring look at the real effects of cancer in youths.
Esther was a young American writer and vlogger active in the Nerdfighters (a community created by John and Hank Green) and the Harry Potter Alliance. At the age of 12, in 2006, Esther was diagnosed with metastasized papillary thyroid cancer, and a year later doctors declared that it was terminal. She remained active in these online communities, meeting Green in person at least once and continuing an online friendship with him for three years. Esther died August 25, 2010 at age 16.
Green and the Nerdfighter community started a remembrance to her on August 3, 2011, which would have been Esther's next birthday. The day was called Esther Day and, in accordance with Esther's wishes, it was celebrated as a day about love between friends and family. John's eulogy upon Esther's death and his videos on Esther Day in the years after can be found on the Vlogbrothers YouTube channel.
Esther's family also started a non-profit, publicized by Green and the Vlogbrothers, called This Star Won't Go Out (http://tswgo.org/), which "is making a difference in the lives of children with cancer, one family at a time. By providing funds to help pay for travel, a mortgage or rent check, and other cost of living expenses, TSWGO frees up families to focus on their child who is in treatment."
Finally, Esther’s parents posthumously published a book of her writings, titled This Star Won't Go Out: The Life and Words of Esther Grace Earl. Green wrote an introduction to this book. The book won the 2014 Goodreads Choice Award in "Memoir & Autobiography." The book contains a biography of Esther's life, short pieces of writing, journal entries, and drawings.