Attack of the Not-So-Virtual Monsters (Gamer Squad 1): Gamer Squad #1 by Kim Harrington
Bex and Charlie love playing the popular mobile game Monsters Unleashed. They even check out an antique map in the attic in hopes of discovering forgotten places where the rarest monsters might hide. But there's a strange machine up there too. When Charlie switches it on, the WiFi goes down . . . and Bex's monsters escape from her phone into the real world! Can the friends nab the beasts before they become monster lunch?