+1 for anything by Feynman (as a point of interest, it was noted in 'Free as
in Freedom' that Stallman was influenced by Feynman - maybe this accounts for
some of his personality traits e.g. a loathing of honors and authority).
As for some recommendations, anything by Carl Sagan is absolutely terrific.
'Cosmos' is the all-time classic, but I also found 'Pale Blue Dot' and
'Dragons of Eden' terribly interesting too.
Also, for more free software literature, 'Code 2.0' is a great book about the
evolution (or potential devolution) of digital technology by Lawrence Lessig.
