This classic of world spirituality recounts an anonymous 19th-century Russian peasant's attempts to follow St. Paul's advice to "pray without ceasing." In addition to its profound theological and philosophical observations, it offers an authentic portrait of Russia's social conditions during the final years of serfdom.
Here's a sample of other books in this Dover category
The Practice of the Presence of God and The Spiritual Maxims by Brother Lawrence This simply written little book about prayer and Christian life combines two classics in one — each a primer of practical Christian devotion that beautifully conveys the thoughts of a 17th-century Carmelite monk.
The Kingdom of God Is Within You by Leo Tolstoy, Constance Garnett The soul-searching book that inspired Gandhi to embrace the concept of passive resistance, Tolstoy's 1894 polemic clearly outlines a radical, well-reasoned revision of traditional Christian thinking.