This depends a bit on the scale of your startup and where you want to focus. As the startup develops, if you will be building, growing, and directly managing the technical team then a focus on people books is appropriate (e.g. "Peopleware" and my personal favorite "Turn the Ship Around").
If you are also leading product, then "The Principals of Product Development" is an excellent book.
If you are tasked with research and innovation then "The Innovator's Dilemma" is a must read.
Happy to share more recommendations if you get in touch.
