Close Encounters of the Nerd Kind (Gamer Squad, Bk. 2)

After their monster-catching adventure, Bex and Charlie vowed never to play Monsters Unleashed again. But that doesn't stop them from trying a new augmented reality game, Alien Invasion. Even their science teacher loves it, because when you hold your phone up to the night sky, a star map fills in, teaching players about astronomy while they capture virtual extraterrestrials.

Then the class goes to an observatory on a field trip, and Bex accidentally summons real extraterrestrials to town through the app! Alien Vera is sweet, kind, and curious, but her mischievous alien students are running rampant around town. And then there's Bob, who's less sweet . . . and more evil. Can the Gamer Squad capture them all before any earthling or extraterrestrial is harmed - and figure out a way to send the aliens back to their home planet.