“A Race For Madmen” by Chris Sidwells has been mentioned already but it’d be a great introduction for anyone wondering what the big deal is about the Tour de France.
Also second the recommendation for “Kings of the Mountains” – Matt Rendell does a great job of explaining a country’s cycling mythology without destroying its appeal.
Riders’ autobiographies are generally a bit heavy on the ego and self justification, but Tom Simpson’s book “Cycling Is My Life” is an exception. He was clearly insanely driven (he literally rode himself to death after all), but still oozes charm. “Les Nomades Du Velo Anglaise” is a similar relic of a bygone time when cyclists could also be Chaps.
Fignon and Millar’s books are interesting in a different way, given that they spent much of their careers dealing with very high profile failures.