An excellent overview, substantially illustrated.
The description of the November 1967 X-15 crash is harshly written towards the pilot Major Mike Adams, possibly reflecting the language of the NASA official report. Mike Adams did get the X-15 out of the spin before it disintegrated. Perhaps blaming a pilot no longer there was a way for NASA technical staff to minimise the computer malfunction earler in the flight. I felt the author could have stepped away from official style language describing that fatal incident; putting in that Adams did get out of the spin was something though.