* Extreme Programming Explained by Kent Beck
* Clean Code and The Clean Coder by Robert C. Martin
* Soft Skills by John Sonmez (1st edition)
* Pragmatic Programmer by Andrew Hunt and David Thomas
* Working Effectively with Legacy Code by Michael Feathers
* The Mythical Man-Month by Frederick Brooks
(Selfish plug) Additionally, I wrote my own book concerning the entire industry, from just starting out to becoming a self employed consultant when you get sick of fulltime work - all soft skills from my decade or so of the industry, as well - https://www.amazon.com/dp/B0B43V1JJW