Answer to the title question but not the second one: I decided to go into computer science after reading "The Turing Omnibus" by A.K. Dewdney. It was like my brain was let loose in a candy store. I must have been insufferable that summer, always talking about Boolean logic and perceptrons and Turing machines and NP-completeness. Answer to the second question but not the title one: "The Friendly Orange Glow" by Brian Dear is a well-written history of the PLATO computer system and, most importantly, of the community that grew around it.
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