A decent read, but I much prefer his "Personal Observations on the reliability of the Shuttle" http://www.ranum.com/security/computer_security/editorials/d....
It's of a lot of interest beyond simply the direct information about the space shuttle, mainly because of its discussion of reasonable risk taking, how to measure very remote probabilities, and the potential for a large disconnect between engineering and management with regards to safety measurement. And then of course it's about the space shuttle, so that's awesome.