The Enchantress Returns by Chris Colfer

Welcome back to the land of fairy tales! The magical land of stories is plagued by a dark threat: the evil sorceress is back, and she has kidnapped Alex and Conner's mother in order to blackmail their grandmother. The twins must travel through a portal to the magical land again or they may never see their mother again! Soon they are looking for a rare artifact, the so-called Staff of Wonder. In order to harness his power, the siblings must embark on a journey to the most feared places in the entire magical land - this is the only way they can stop the sorceress!