Incredible, terrifying, difficult. So many reviews have been written that I don't feel I have much to add. Everything about this book, really -- the structure, the writing style, the character development -- worked for me. It is clear to me, as someone with a background in archival research, that a lot of historical research went into this book, with clear parallels to actual historical places/events despite being a work of fiction. In some ways I wish more had been done with the railroad itself -- here a network of trains -- but really, it wasn't the focus: the lives of those who made it happen, those who traversed it in their escapes and those who supported them along the way, were the real focus here. It was a difficult read, and an important one. This is the second novel by Whitehead that I've read and I've already added another to my list -- highly recommend.
Content warning: This is a novel that is very much rooted in the history of slavery in the United States; as such, it is entirely pervaded with a sense of terror + dread and depicts the horrors of slavery. More specifically: warnings for graphic violence, sexual violence, mass murder, gun violence, medical experimentation + eugenics, lynching, genocide