The book was aimed at decreasing the fear of night in children by basically telling them that monsters were just as afraid of humans as humans were of monsters. The book received good reviews after it came out, with hardly any review lower than a 75% rating on any book review site. Some of the books came with an extra plush toy of Dennis with his pillow and teddy bear in each arm. An animated adaptation of the book was broadcast on September 9, 1989 as one of the "ABC Weekend Specials". The introduction starts the book in the setting of a small picnic of a human and his dog. The human is apparently telling the reader to not venture into the Withering Wood, a forest of trees rumored to have legendary creatures such as "hairy trolls, nasty gnomes, and scary pixies and fairies." The book then changes setting into inside the forest, where we see a small monster named Dennis and his mother, showing that Dennis was very polite for a young monster. It describes Dennis's fear of humans, which leads to the next part of the book. Dennis screams and shouts he will not go to bed. The mother, surprised at this sudden fear of bed, asks why. Dennis explains that he is afraid of humans. He says humans will "creep under my monster bed while I'm asleep." Dennis's mother is not convinced of her son's story and tries to persuade Dennis to fall asleep. She gives Dennis his teddy bear and also says she will not turn off the light. She begins to kiss Dennis, but Dennis reacts and bites her on the nose. Dennis's mother then promises her son that the humans won't get him. She then readies him for bed. However, Dennis concludes he will sleep under his bed so the humans will not be able to find him. As Dennis falls asleep, a young boy skips school and ventures into the Withering Wood to hide (presumably from his parents). He walks deep into the woods so that he comes upon Dennis's and his mother's cave. Not knowing where he is, he walks into the cave for rest. He then decides to sleep. He finds Dennis's bedroom and decides to sleep on the bed. He changes into his night clothes and begins to fall asleep. However, the boy was afraid of monsters. With the absence of his mother, he checks under the bed himself, and to his surprise, he finds Dennis. Both Dennis and the young boy run away. The book then explains not to misbehave and how it would feel if Dennis's mother would tell the reader if humans were not real.