This isn’t the book you’re looking for.
First, the book is for students in Gov 1005: Big Data, a course offered in the Government Department at Harvard University. Everything about the book is designed to make the experience of those students better. I hope that some of the material here may be useful to people outside of this class.
Second, the book changes all the time. It is as up-to-date as possible. The later chapters are still in draft.
Third, I am highly opinionated about what matters and what does not. You might not share my views.