The Book of Legends by Lenny Henry

Twins, Bran and Fran, are two ordinary kids who are about to go on an extraordinary adventure!

When their mum mysteriously disappears in a lightning strike, just like their dad, the twins are all alone and know they have to stick together - if only to face their new guardian's terrible cooking! But when their mum's treasured storybook turns out to be a portal to another world full of mythical legends, everything changes. Suddenly, evil princes, mud monsters and Viking armies are all very real and out to get them.

Luckily, the twins have Wilma, the Wizard's Wife, and Zachary, a wisecracking Zebracorn, to help them solve the mystery surrounding their parents' disappearance. Quests are no joke (but there are lots of jokes in this book) and this is the quest of a lifetime . .