Seo gives a dispassionate review of 4th amendment law as it intersects with traffic stops and the automobile. The kernel of an idea is interesting, and the book is well-researched, but it reads like an extended law review article and misses a big opportunity to explore what the history actually means. I'm rounding up because of its core insight and wealth of data, but I found it to be as dry and unenjoyable a read as a book on civil rights can be.
The first part of the thesis relates to how the automobile changed the nature of policing, and this is covered in the first two chapters (at length). Everything that follows then is basically about how policing the automobile changed 4th amendment law. Because the book essentially just follows legal outcomes, Seo actually goes out of her way to frame the story as a battle of Everyman, since jurists were not concerned with discriminatory policing but arbitrary policing. Apart from the occasional anecdote, it doesn't even actually get to discriminatory policing until basically the very end of the last chapter before the epilogue.
The writing is exceptionally dry and academic. There are only two parts of the book that aren't basically a "this and this and this" rundown of legal history, both of which still follow that format: the opening chapters (which is a pretty linear history of mostly August Vollmer, who was a major figure in professionalization of the police force, and its motorization), and a chunk in the middle that just had paragraph after paragraph from incidents in ACLU and NAACP files of individuals questioning their own traffic stop experiences. Otherwise, it's a rundown of case details and outcomes, written by a lawyer.
The book really misses a huge opportunity to say something. Essentially, the big point is made in Chapters 1 and 3, and the rest of the book is just watching the slowly unfolding ramifications of those two events (Chapter 2 in particular feels exceptionally redundant with Chapter 1). IMO, Seo misses a huge opportunity to actually comment on the legal outcomes - she essentially has made the case for an "original sin" in 4th amendment law, that of Carroll v. United States which could have defined the car as a private space but chose instead to treat it publicly, which led to a host of "reasonableness" infecting every aspect of how the car inhabits this gray area. However, she never actually uses this frame -- she doesn't suggest that the law got it wrong, nor does she even explore the ramifications of an alternative outcome, even though it is really the lynchpin of her book. Even though she repeatedly calls back to Carroll, she doesn't even try to draw a summary straight line through the major cases referenced to really bring home how this chain of events led to discriminatory policing. To me, this all feels like a massive missed opportunity to actually flesh out the design and intentionality of what has transpired or what could have instead, and instead Seo goes out of her way to not say anything and let the legal texts stand by themselves. This is beyond frustrating.
At the end of the day, I don't think I'd recommend this book to folks without an interest in 4th amendment law. It is so drenched in legal text, down to the author's completely dispassionate writing style, that it turns a discussion of civil liberties into something that is downright boring. The core of the book is a brilliant insight, but the desire not to do anything but flesh out that insight neuters the book's impact.