Raising Steam (Discworld Book 40) by Terry Pratchett. Involves trains.
Underground: A Human History of the Worlds Beneath Our Feet by good Will Hunt. Involves caves, subway stations, bunkers, and such. I don’t know the book, stumbled across it, looked interesting.
I can recommend both of them, although the Pratchett book is one of his less good
Discworld ones, just that he was also obsessed with Victorian era steam trains.