The Pillow Book is a book written by Sei Shōnagon . Sei Shōnagon was a member of the Kiyohara family. She wrote the notes that made up her diary (or "pillow book") while she was a member of the court of Empress Sadako. The book is a classic of Japanese literature. It is one of two of the greatest examples of prose literature of this time period. It is a collection of pieces of writing that vary from one or two sentences to several pages. It is the author's observations of people, life at court, and nature.