The novel that started the series, "Gossip Girl," was published in paperback format in April 2002. Two new novels were released annually until the final novel, "Don't You Forget About Me", was released in May 2007, showing the main characters graduating from high school and moving on to college and other pursuits. A prequel novel, "It Had To Be You", was released in October 2007 in hardcover and electronic book format. It detailed the events that occurred a year before the first novel. A box set containing the eleven novels of the series and the prequel novel, in paperback format, was released November 1, 2009. Two days later, a sequel novel, "I Will Always Love You" was released. The hardcover book tells the story of the main characters returning home from college for the holidays. Hachette Group re-released all of the original novels in electronic book format between 2008 and 2009.