What is the author's style in Operating Instructions by Anne Lamott?

One aspect of Operating Instructions that many reviewers commented on, and which will likely strike many readers as well, is its humor. Lamott's reflections are witty, irreverent, and astute. She uses humor as a means of expressing her thoughts about life, which are often earnest and somber, without becoming pedantic or heavy. For example, in the book's first few pages she wonders how anyone can have a child knowing that eventually that child will have to go through the seventh and eighth grades.