Augustine, Confessions

Kempis, Of the Imitation of Christ

Pascal, Pensées

If you purchase this book, make sure to get the edition that is edited by A.J. Krailsheimer.  For some reason, Amazon is not allowing me to link to that edition.

Bunyan, The Pilgrim’s Progress

Kierkegaard, Purity of Heart is to Will One Thing

Chesterton, Orthodoxy

Lewis: Loads to pick from, but I choose Surprised by Joy