I highly recommend as an introduction Alan Watt's 'The Way of Zen', that covers, in great detail, the cultural background, history and practice of Buddhism, in its prominent forms, and its roots in India / Hinduism -- all of which are necessary to comprehend even basic 'traditional' buddhist literature, after having become so institutionalized over the centuries as to have obscure many of the original, and plain to state, insights with now archaic ways of thinking but nevertheless have been maintained essentially untouched.

Then, follow your nose through the bibliography. =)