Not mathy, more where philosophy is coming from, but the books I remember from about the same timeframe as GED were Penrose's The Emperor's New Mind Timothy F

Not mathy, more where philosophy is coming from, but the books I remember from about the same timeframe as GED were Penrose's The Emperor's New Mind Timothy Ferris Coming of Age in the Milky Way and the Zen and the Art of Motorcycle Maintenance, previously mentioned. Maybe not the most current thinking (but perfectly fine as an introduction), but the writing is more accessible than GED.