Dragon Mountain ( Dragon Realm 1 )

"When 12-year-old Billy Chan finds out his parents are sending him to a language and culture camp in the middle-of-nowhere China, he can't imagine anything worse. He's not expecting to become friends with fellow campers Dylan O'Donnell, Charlotte Bell, and Liu Ling-Fei. And he's definitely not planning to meet any dragons. But when the four kids accidentally open a crack in an ancient mountain, they become involved in an ages-old struggle of good versus evil. Now it's up to them to save the Dragon Realm--if they don't, the world as they know it might disappear forever"--