When I first listened to this book about 4 years ago, it was the epitome of how I wanted to interact in an organization. The story of a fail multi-hundred million dollar project done by a government contractor using waterfall, juxtaposed with a early delivered, highly successful project done using Scrum caught my attention. I wanted to work in a company that followed the Scrum principles and lived by an ethos of transparency, both internally, as well as externally.
Now I have realized that many companies don't follow scrum in this exact way, but this was the book that taught me some core principles:
Deliver Early and Often and Get Feedback
Estimation is a Joke
Projects have failed with the best of plans
You only need to deliver the highest value items, not a perfect system