If you want an extremely engaging, well-researched introduction to the roots and ongoing dynamics of the United States' empire - territories that have inhabited a legal and social grey area from the perspective of the mainland US - this book is a one stop shop. Immerwahr lays out the surprising motivation for many of the US's territorial acquisitions (seriously, there's a whole chapter that centers on the importance of guano for agriculture), as well as the not so surprising (Teddy Roosevelt's desire to cosplay Daniel Boone). Beyond that, Immerwahr exposes the hypocrisy that has continually followed the United States from its inception - its claim of representative democracy and equality for all while excluding peoples and places from that ethos.

Mixed in are anecdotes and sections around these topics that are fascinating, even if they don't further the main aim of the book (did you know Herbert Hoover fished while wearing a suit and tie?). Also the section on the discovery of ammonia synthesis by Franz Haber and his subsequent scientific efforts/personal life literally moved me to tears. Highly recommend.