Principia Mathematica by Whitehead and Russell (1910) reads modern despite its age. The massive work explores foundational mathematical concepts with surprising contemporary relevance. It discusses referential transparency, extensionality, and type theory—introducing terms like "domain," "alpha renaming," and "type" in their modern sense.

The text anticipates lambda-calculus through its treatment of propositional functions and schematic variables. With nearly one thousand pages proving that 1+1=2, the book features excruciatingly detailed proofs that avoid hidden premises. The goal was establishing minimal basic notions sufficient for all mathematics—the bulk found in the Preface and Chapter 1.

Readers find it both engaging and difficult to put away, containing insights into intuitionism, freedom versus binding of variables, and substitution principles. The notation system anticipates control operators and context-dependent expressions. While dense, the fundamental framework remains accessible.