Some helpful resources for angel investors:

Venture Deals: Be Smarter Than Your Lawyer and Venture Capitalist by Brad Field and Jason Mendelson
”The book dives deeply into how deals are constructed, why certain terms matter (and others don’t), and more importantly, what motivates venture capitalists to propose certain outcomes. You’ll see the process of negotiating from the eyes of two seasoned venture capitalists who have over 40 years of investing experience as VCs, LPs, angels, and founders.” (Amazon)

Zero to One: Notes on Startups, or How to Build the Future by Peter Thiel and Blake Masters
Zero to One is about how to build companies that cre­ate new things. It draws on everything I’ve learned directly as a co-founder of PayPal and Palantir and then an investor in hundreds of startups, including Facebook and SpaceX. But while I have noticed many patterns, and I relate them here, this book offers no formula for success. The paradox of teaching entrepreneurship is that such a formula necessarily cannot exist; because every innovation is new and unique, no authority can prescribe in concrete terms how to be innova­tive. Indeed, the single most powerful pattern I have noticed is that successful people find value in unexpected places, and they do this by thinking about business from first principles instead of formulas.” (preface)
A weekly newsletter/blog analyzing strategic trends in the startup and tech world.

Andreessen Horowitz blog and podcast
Thoughts from a prominent Silicon Valley VC firm.