This via r/programming today: A non-standard book list for software developers:

• Euclid’s Elements
• Calculus, 4th edition (the article above references the 3rd edition, not sure why, also there is an answer book)
• Operating System Design: The Xinu Approach, Second Edition
• Lisp in Small Pieces

Also some bonus material mentioned: Calculus Revisited: Single Variable Calculus video lectures from the late MIT lecturer Herb Gross.