Twilight is a series of four vampire-themed fantasy romance novels by American author Stephenie Meyer. It charts a period in the life of Isabella "Bella" Swan, a teenage girl who moves to Forks, Washington, and falls in love with a 104-year-old vampire named Edward Cullen. The series is told primarily from Bella's point of view, with the epilogue of Eclipse and Part II of Breaking Dawn being told from the viewpoint of character Jacob Black, a werewolf. The unpublished Midnight Sun is a retelling of the first book, Twilight, from Edward Cullen's point of view. The novella The Short Second Life of Bree Tanner, which tells the story of a newborn vampire who appeared in Eclipse, was published on June 5, 2010 as a hardcover book and on June 7 as a free online ebook. The Twilight Saga: The Official Illustrated Guide, a definitive encyclopedic reference with nearly 100 full colour illustrations, was released in bookstores on April 12, 2011.
Since the release of the first novel, Twilight, in 2005, the books have gained immense popularity and commercial success around the world. The series is most popular among young adults; the four books have won multiple awards, most notably the 2008 British Book Award for "Children's Book of the Year" for Breaking Dawn, while the series as a whole won the 2009 Kids' Choice Award for Favorite Book.
Source: Wikipedia, "Twilight series", available under the CC-BY-SA License.