What follows is a bullet point summary of what I thought were the most important parts of this book.
Question your assumptions
If you're interested in startups and you haven't heard of "The Four Steps to the Epiphany" by Steve Blank you should definitely check it out. I would describe it as a process to help steer a startup through the chaotic path to profitability and success. "The Four Steps" reads a lot like a university textbook, leaving some recent Customer Development converts in search of a more readable summary.
This is where The Entrepreneur's Guide to Customer Development comes in. The most important thing to note about this book is that it focuses entirely on the first phase of Customer Development: Customer Discovery. There are actually four stages of Customer Development:
I felt that that the aim of this book was to provide a gentler introduction to Customer Discovery. A good analogy for this book would be CliffsNotes for Customer Development. At a slim 74 pages or so, it gives you a set of actionable items that you can implement immediately, and presents this information in a much more conversational tone. I found it a much easier read than the Customer Discovery chapter in "The Four Steps".