During the event of Niconico Live yesterday, light novel series Nisemonogatari (偽物語) was green-lit for Anime adaptation. Continued by Bakemonogatari (化物語) and Kizumonogatari (傷物語), Nisemonogatari is the third light novel written by Ishin Nishio (西尾 維新) to be made into Anime. It will be aired in January 2012. The story is set in the early 21st century as a sequel to Bakemonogatari, and it centers around the Fire Sisters Tsukihi and Karen Araragi.
The first trailer was streamed on the official website, check it out.