[bentley]

Can you provide any specific recommendations?

[wyclif]

Sure, how about some classics like:

The Didache

Anselm, Cur Deus Homo

Anselm, Proslogion

Augustine, City of God

Augustine, Confessions

Augustine, On Christian Doctrine

William Law, A Serious Call to a Devout and Holy Life

Luther, The Bondage of the Will

Calvin, Institutes of the Christian Religion

Pascal, Pensées

All of these are in public domain.