The Steam Special Edition includes additional content around the DG2 in-game and behind-the-scenes stories. If you purchase or upgrade to the Special Edition you will receive: - A Matter of Endurance: a 30 minute flash-based audio play that runs on your PC featuring character voices and concept art from a new original story by Hugo award author Mary Robinette Kowal, that takes place between the events of Defense Grid: Containment and Defense Grid 2, - A 312 page PDF of the book "The Making of Defense Grid 2: The complete story behind the game" by Russ Pitts, a reporter and author embedded with the development team during the full development cycle of the game, - A 73 page PDF of the art book: The Art of Defense Grid, showing concept art during the development of the original Defense Grid, and - a 123 page PDF of the art book: The Art of Defense Grid 2, showing concept art developed during the development of Defense Grid 2.