There are a few volumes that deal with the USA's research aircraft programmes out there, most of which are either highly technical, 'dry' treatments or self-serving autobiographies with axes to grind. Thankfully, with one major exception, Evans' book is neither of those.
Adopting a format using each chapter to covey a different test pilot's flights in the X-15, what is presented is human-centred view, bringing out the people and personalities around the programme rather than a detailed, aviation 'buff' perspective. The book reflects what could only be described as voluminous interviews with the pilots, ground staff, and associated people, including the families of those concerned.
A different perspective emerges than the usual one portrayed in popular media; one of hard work, disappointment and frustration interspersed with moments of success and joy, together with the truth that the X-15 was, for most of those involved, merely one part of longer careers.
The only fault I could find in the book was a brief section on Pete Knight's post military career and the clash with his son over Proposition 22 and his anti gay, lesbian and trans-gender rights. Although a part of the post test flight story, the four pages devoted to it smack more of the author pushing an issue rather than something the general reader would care about.