Ken Levine, the creative director and co-founder of Irrational Games, has begun writing for a new game. He tweeted that "Game writing this afternoon. This is something else" and when asked what he was doing for inspiration he replied "What do you do for inspiration? --mad men, pt Anderson, Coen Bros, Kubrick, soderbergh, Stoppard, Sondheim, games".
No other information has been given yet. Ken Levine is well-known among the gaming community as the lead developer in notorious titles such as BioShock, BioShock: Infinite, System Shock 2 and Thief: The Dark Project. He was named one of the "Storytellers of the Decade" by Game Informer.
Source: Ken Levine