More interesting than just a look at pronouns grammatically, this is really a psychology book about how we put our words together (and what that can tell us), encompassing the class of “function words” (including pronouns) that make up a substantial part of our speech. Because of the role that function words play in establishing the structure we use to fill in the rest of the words we use (i.e. nouns, verbs, words with primarily semantic content), Pennebaker looks at patterns in function word frequencies and finds strong correlations with interesting real-world classifications: personality types, rhetoric, political speech, gender differences, even income and education gaps. Elucidating these various correlations forms the majority of the book.
Using function word analysis and modern Natural Language Processing techniques, Pennebaker shows how you can make predictions about the author of an anonymous text, and perform simple culturomics (e.g. gauging national “mood” after the 9/11 disaster) by surveying the text of blog posts across on the internet, all without recourse to more complex semantic information.
A recommended read for anyone interested in psychology and language, and also for those curious to see what modern technology applied to language analysis can tell us about ourselves.