I'll say this right off the bat: Out of the 56 books I've read since starting my professional career, this book has easily been the most useful. I think the only person I've found to be anywhere as helpful might be Gary Bernhardt and his Destroy All Software set of screencasts.
The striking thing about this book is just how much it does not focus on computer software. As the book is focused towards software engineers who wish to be entrepreneurs, it assumes you know software and want to learn about the other aspects of starting a company, such as the importance of product management and marketing. It's also striking for how many hard metrics it provides; you need to launch within six months of having a landing page up and running, your conversion rate may vary between X%-Y%, etc.
I'm a wantapreneur. I have problems with commitment. If I were to start a company though, I think this would be the reference book sitting closest to me.
If this book sold for $100 instead of the $25 on Amazon, it would still have been worth it.