High Quality Content by WIKIPEDIA articles! The Monster Bed is a children`s book by Jeanne Willis and illustrated by Susan Varley that revolves around the twist on the common "monsters under the bed" story that frighten children. The book is a young reader, normally aimed for 4 years or older. The main character, the monster Dennis, believes that human children are under his bed and will get him as he falls asleep. His mother, however, tries to get him to go to sleep. Eventually, a human child accidentally ventures into their home cave, and both the human and Dennis discover each other, frightening both.