In a previous post I quoted C. S. Lewis on the value of reading old books. He argued that every generation has its blind spots, and one way to see past the contemporary blind spots is to read old books. In that spirit, here are some of my favorite old math books.
These books contain useful facts hard to find elsewhere. More importantly, they embody an approach to mathematics that has fallen out of fashion. I believe the latter is what Lewis had in mind, not merely reference books but books that encapsulate the perspective of an earlier generation.