This essay describes the serious humor in The Pillow Book. I think it is a quite interesting question to consider, Sei Shonagon is an interesting person. She writes about nature, about festival, her friends, her life, and it’s like an intelligent woman being sarcastic and talking to herself, which is kind of cute.
http://www.kyotojournal.org/the-journal/in-translation/on-translating-a-classic/
The Heian Court ----- Lady Murasaki and Sei Shanogan 