1. Never Split the Difference by Chris Voss
From someone who hated negotiation books and didn't want to "win" negotiations, this was a true life changer. Listen with empathy. Find the thing your counterpart really wants. Put them in your shoes by asking how you can do [x thing they're asking]. Fundamental things that have improved my relationships with many people in my life.
2. Radical Candor by Kim Scott
This book helped me understand how to care for someone while still challenging them and asking for their best work. I truly believe that people are happier and more fulfilled when they feel challenged by their work and empowered to rise to that challenge.
3. Building a Story Brand by Donald Miller
Selling anything is about understanding that the buyer is the hero of their own story, and your job is to sell them the tool helps them succeed. The buyer is Luke, you're Obi Wan, and you're selling them the Lightsaber. This has been endlessly applicable working with entrepreneurs.
4. The E-Myth Revisited by Michael Gerber
A seminal text on why small businesses often fail and how they can create systems that work and create ongoing success.
5. Non-violent communication by Marshall Rosenberg
This one literally changed who I am as a person and how I show up for others. Realizing how much judgement is embedded in our language, how often we express that judgement to other people, and how that makes them feel was eye-opening. I strive to both feel and express radical non-judgement, and to listen to and communicate with people in a way that allows them to feel heard and safe.
I have strong, loving relationships with some people in my life that I never would have expected 10 years ago, in part because this book helped me grow.