(How can you review a new release, well getting access to it pre-publication helps - just lucky, not a friend of either author).
Brad Feld is one of the most qualified people I know of to write on this subject, from actually walking-the-walking to being passionately involved in many and various ways with entrepreneurs and founders throughout the US and globally he has the perspective and credentials to write this book. I am sure this is true for Ian too, I just have not followed his achievements.
The book is a true analysis, with detailed conclusions but also detailed reference for the reader to look at the data on which the book is built. Indeed this is probably the most cross-referenced book I have read in many years. From chapter notes with links to all kinds of sources (in the Kindle version), to the it's own detailed, linked index - it's an analysts dream. Too much, I don't think so - though much will be lost to the Audible reader (which is how I usually consume books).
This book covers a long history, but is not a simple rework of old material which is updated and added to - it is current perspective on historic observation - if only others were learning from history and re-evaluating as they went!
Who is this book for? It seems everyone in the startup community but especially those trying to actively grow and engage such communities - it's for 'activist' founders (which is many of course), not just founders. Not your typical book about startups - don't bother if you are a wannabe founder looking for more reading to take no action upon.
I've enjoyed Brad's perspectives via his blog for a long time, this book has a very different feel to it - for which I assume we thank Ian. Great research, great context and timely as the global economy tasks another big shift in response to 'new wormal'.