The Divide — Elizabeth Kay

A unique and humorous fantasy that weaves a cast of eccentric and charming characters into an incredible adventure story.

When Felix's parents take him to "The Divide"--a spot in Costa Rica where the waters that run down to the Pacific and Atlantic oceans separate--Felix finds himself in a bizarre parallel world where mythical creatures and magic are a reality.
There, he meets Betony, a tangle child and herbalist who becomes his friend in this strange land. As Felix explores this new world he soon discovers that its mythical beasts and fairy folk think Felix is a legendary creature who uses practical science instead of magic! Will Felix ever find his way back home...and will he want to?