A pretty good read. I very much agree with the central points of the book: rapid iteration, small batches, actionable metrics, learning as progress, and above all, following a scientific method when building a startup. The book occasionally sounds a little bit like an infomercial, but for the most part, it's well balanced, and Eric Ries stresses the point that the magic is not in any specific terms or processes he coins, but in the general theory/idea of following a scientific process.
Some fun quotes:
"Because startups often accidentally build something nobody wants, it doesn't much matter if they do it on time and on budget. The goal of a startup is to figure out the right thing to build - the thing customers want and will pay for - as quickly as possible."
"I've come to believe that learning is the essential unit of progress for startups. The effort that is not absolutely necessary for learning what customers want can be eliminated. I call this 'validated learning' because it is always demonstrated by positive improvements in a startup's core metrics."
"In fact, entrepreneurship should be considered a viable career path for innovators inside large organizations. Managers who can lead teams by using the Lean Startup methodology should not have to leave the company to reap the rewards of their skills or have to pretend to fit into rigid branches of established functional departments. Instead, they should have a business card that says simply 'Entrepreneur' under the name."
A quote in the book from Peter Drucker: "There is surely nothing quite so useless as doing with great efficiency what should be done at all."