Rowan of Rin - by Emily Rodda

Is young Rowan up to the task of saving his village from an unknown fate? The boy certainly hopes so, as he sets off with the strongest villagers (against their better judgment) to discover why the river their village depends on has begun to dry up. As the group climbs the mysterious mountain, all kinds of strange things happen, and only the strongest survive. This is a fun mystery, full of magic and adventure. There are two sequels, though I haven't read them. This book is good enough to stand on its own, no question. Read this if you like mystical adventures, with riddles, danger, and strange enemies.

This author also wrote the Deltora Quest series.