Britney Spears was back in fine form when she hosted the Wango Tango music festival in Carson, CA, yesterday. She was joined by her former kindred X Factor judge Demi Lovato as well as performers Avril Lavigne, Bruno Mars, and Maroon 5's Adam Levine. Britney wore a formfitting black dress as she took the stage to introduce the acts, marking her first onstage appearance since she left The X Factor back in January. While she didn't perform this time around, Britney fans will get a chance to see the singer perform live soon as she confirmed last week that she will be taking up a residency in Las Vegas. The concert series, which will reportedly be held at Planet Hollywood, will begin in the Fall. Preparing for Sin City isn't the only thing on Britney's mind — she recently tweeted that she is reading The Goddess Inheritance, a YA novel by Aimee Carter.