I always thought that the most difficult part of a space mission was the technical one. Building a machine that could travel millions of kilometers during a decade or more without blowing up.
After reading this book, I believe I was probably wrong. The hard part is the political one, all the effort required to get the mission approved and funded. I really could not believe the amount of approvals and consequent cancellations the New Horizons mission went through, the political machinations it had to overcome. Personally I don't think I could have found the energies to persevere through all that. Dr. Stern (the mission lead) and his team were true heroes for that.
I you're interested in space exploration, this book is a must read. It provides a great insight on the effort required to successfully complete a space exploration mission. Spoiler: it's probably a much bigger effort than you thought. It also sheds light on the human part of a space mission, the
people involved and the sacrifices they had to endure in the name of space exploration.