The Philosophy of Money
Money as abstraction and culture.
Simmel wrote this in 1900 and it remains the deepest account of what money does to human consciousness and social relations — how the universal solvent of monetary exchange dissolves particular bonds and replaces them with abstract equivalences. It is not a comfortable book for anyone who builds financial systems, but it is an honest one: financial infrastructure shapes how people relate to each other and to the world, not just how they transfer value.