Why do people need to sleep? What happens when you are asleep? And where do different animals sleep? Find out in Sleep. The fiction book that accompanies this title is Wake Up!. Oxford Reading Tree Explore with Biff, Chip and Kipper is a series of paired fiction and non-fiction books linked by curriculum-related topics.Each pair consists of an engaging story featuring well-loved characters and a compelling non-fiction book.These topic-linked pairings will develop and deepen their reading comprehension and foster a love of reading across both text types.This book is one of six titles at Oxford Level 9, which are phonically decodable featuring vocabulary to enrich the texts and support language development.All the books in the series are carefully levelled, so it is easy to match every child with the right book and enable them to progress.