NASA chosed Dennis R. Jenkins book "X-15: Extending the Frontiers of Flight" to launch its series of pdf e-books especially formatted for dedicated e-book reading devices like Amazon's Kindle.

X-15 in itself is one of the most amazing aerospace programs. It was extremely ambitious and technically challenging. It established the foundation of high speed and high altitude controlled flight through the flights of 3 X-15 aircrafts in a program that lasted about 11 years and it is still highly valuable even today.---



It was also very dangerous for the test pilots and claimed the life of test pilot Michael J. Adams (tragically while his family was invited to watch that specific flight). As Milt O. Thompson states in his book about the X-15 program, there was a saying that the job of a test pilot is countless hours of boredom interrupting by moments of sheer terror while the X-15 programs was countless hours of terror interrupting by moments of sheer boredom.

I haven't still read Dennis R. Jenkins book but I bet it (after I browsed it briefly) that it would be an excellent and informative read.

NASA link for kindle e-books
NASA link for "X-15: Extending the Frontiers of Flight"(kindle pdf version)
NASA link for the pdf of the print edition

Both pdf files are of course freely available for downloading.