Goodnight Moon is considered a classic in children's literature. The book is a poem, written in a simple rhyme form. It contains illustrations of many objects familiar to a child, including a reoccurring mouse. Part of the activity of reading this book is identifying these objects in the illustrations. As the book progresses, the room depicted gets continuously darker, the moon rises higher in the sky, and the time on the clock gets later.
It is published in a board book edition, a book whose pages are actually stiff cardboard to make it suitable to give to a very young child. It is also published in a 'jumbo' edition, suitable for use with large groups.