The pre-astronauts: Manned ballooning on the threshold of space includes Joe Kittinger's amazing jump from over 102,000 feet. The second book, Magnificent failure (also by Craig Ryan) is about Nicholas Piantanida who died during a high altitude balloon mission (summarized below in an excerpt from a Wired article):
Skydiver Nicholas Piantanida tried to break Kittinger's unofficial record three times, beginning in 1965. On the first attempt, a 6-knot wind decapitated his balloon at 22,700 feet. On his second attempt, Piantanida couldn't disconnect from his onboard oxygen.One of the high altitude pioneers profiled in The pre-astronauts is Jean Piccard. Wikipedia reinforced my suspicion that Star Trek's Jean-Luc Picard is his namesake.
The circumstances of Piantanida's third and fatal attempt remain baffling. He was still on his way up at 57,600 feet when ground control staff heard a scream and then a monstrous gush of air come through their monitors. Piantanida had lost pressure at 11 miles high. One theory is that he may not have prebreathed sufficiently before taking off, later causing him to struggle for breath, panic, and open his visor. If so, "it was basically suicide," speculates his daughter, Diane Shearin, "like crossing a desert with one canteen."