Ask HN: What is your favorite introductory-level textbook?

Eleven years after graduating I have rediscovered how enjoyable it is to flip through a high quality intro textbook on a topic about which you are curious.

I’ll go first:

Calculus and Analytic Geometry (1951) by George Thomas

It’s readily available for < $10 and I find it’s style much more engaging than contemporary textbooks on the same topic.

And a bonus one - when we had questions for the doctor when my wife was pregnant, I read the beginning of this and can say with reasonably certainty that I reduced the probably of some negative outcomes as a result:

Callen's Ultrasonography in Obstetrics and Gynecology (Mary Norton, 2016)