Sylvia June Day is an American writer. She also writes under the pseudonyms S.J. Day and Livia Dare. Day is the author of the internationally bestselling erotic new adult Crossfire series, which has six million English-language copies in print and international rights licensed in thirty-eight territories as of February 2013. The first book in the series, Bared to You, was declared Penguin UK's "fastest selling paperback for a decade" and Penguin Group (USA) reports that Bared to You is Berkley's biggest breakout book of 2012.