Reckless by Cornelia Caroline Funke

Jacob Reckless was 12 when he found that he could travel back and forth through a mirror into a world that is recognizable from Grimm's fairytales. Fast-forward 12 years, when Jacob's younger brother Will finally manages to follow him into that place, unaware of the many dangers. The tale gets underway when Will starts turning to stone and Jacob is prepared to do anything to save him. He is even willing to risk his relationship with the other love of his life, a shapechanging fox.

As with Funke's Inkheart, this is a story that will appeal to a range of readers from about Grade 5 and up, even though the characters are all adults (and talking animals and dwarves and fairies). Readalikes (especially for teens and up): The Witch's Boy by Michael Gruber; The Book of Lost Things by John Connolly; The Child Thief by Brom (three books that have a similar dark tone - progressively so, in the order listed - and draw on a mixture of European folk tales - as well as Peter Pan, in the case of The Child Thief). Readers looking for an action/adventure tale in another fantasy world with a complex political situation might also enjoy Fire by Kristin Cashore.