The guys over at The Satoshi Nakamoto Institute have compiled a very nice list of literature going back all the way to 1957 with William Fellers 'An Introduction to Probability Theory and Its Applications, Vol. I'
If you're interested in learning about all the genius concepts theorised and developed over the last 60 years that eventually led to the creation of Bitcoin this is a fine place to start.
http://nakamotoinstitute.org/literature/