This book's message could be easily summarized by saying that there are only two kinds of companies: the ones that disrupts, and the ones that are being disrupted. There is no middle ground, and companies that have once disrupted, will soon going to be at the loosing side of the game. Christensen and Raynor do an impressive job in bringing up real world example of disruptions, and the common thinking behind the managers in both companies - the disruptor and the disrupted - that led them to ultimately be in that position. You'll be impressed to learn how much of our common sense decisions are dreadfully harmful to the future of your enterprise, how to recognize them, and how to correct course.
Very important read to any entrepreneur or aspiring entrepreneur. Highly recommend it!