Principia Mathematica is modern and insightful

Principia Mathematica (1910) by Whitehead and Russell reads surprisingly like a modern programming language text, discussing concepts such as referential transparency, extensionality, types, and anticipating lambda-calculus and intuitionism. The work's key contribution lies not in its famously lengthy proofs (taking 1,000 pages to prove 1+1=2), but in its foundational concepts and setup, which established basic notions sufficient for all mathematics using only those primitives.