Catholic Books & Classics Online:
(Note: The following links to Catholic books and writings are located on a number of other web sites, some with questionable theologies and others that aren't Catholic, so only the books on the links below are recommended.)

The Early Church Fathers
(many volumes)

Diary: Divine Mercy in my Soul
St. Faustina

The Confessions of St. Augustine

The Spiritual Exercises
of St. Ignatius of Loyola

Abandonment to Divine Providence
by Jean-Pierre de Caussade

Uniformity with God's Will
by St. Alphonsus Ligouri

The Practice of the Love of Jesus Christ
by St. Alphonsus Liguori

The Great Means of Salvation and of Perfection
by St. Alphonsus Liguori

Story of a Soul
St. Therese of Lisieux

The Three Ages of the Spiritual Life
by Reginald Garrigou-Lagrange

The Spiritual Life: A Treatise on Ascetical and Mystical Theology
by the Very Rev. Adolphe Tanguerey, S.S. D.D. (Also other books on spirituality on this page.)

The Practice of the Presence of God
by Brother Lawrence

The Interior Castle
by St. Teresa of Avila

The Way of Perfection
by St. Teresa of Avila

The Life of St. Teresa of Jesus
by St. Teresa of Avila

The Imitation of Christ
by Thomas, à Kempis

Introduction to the Devout Life
by St. Francis de Sales

Practice of the Love of Jesus Christ
St. Alphonsus Liguori

Summa Theologica
by St. Thomas Aquinas

Treatise on the Love of God
by St. Francis de Sales

Dialog of Catherine of Siena
by St. Catherine of Siena

Divine Mercy in my Soul
The Diary of St. Faustina

Orthodoxy
by G.K. Chesterton

The Sinner's Guide
Ven. Louis of Granada, O.P.

Poems of St. Therese of Lisieux

The Writings of St. Francis of Assisi

Collected Works of Edith Stein,
Vol. IV (Carmelite Nun)

The Dolorous Passion of
Our Lord Jesus Christ
by Anne Catherine Emmerich

Ascent of Mt. Carmel
by St. John of the Cross

Dark Night of the Soul
by St. John of the Cross
Dark Night of the Soul (ICS Version)

The Spiritual Canticle
St. John of the Cross

The Journey of the Mind Into God
by St. Bonaventure of Bagnoregio

On Loving God
by St. Bernard of Clairvaux

Rule of St. Benedict
by St. Benedict,
Abbot of Monte Cassino

Revelations of Divine Love
by Julian of Norwich

The Cloud of Unknowing
by Anonymous

Holy Wisdom
by Augustine Baker

The Little Flowers
of St. Francis of Avila

Treatise on Purgatory
St. Catherine of Genoa

Sermons of St. Anthony of Padua

More Catholic books can be found also at these websites:
www.catholictreasury.info/library.htm

www.CatholicFirst.com

Letters of St. Teresa of Avila

St. Alphonsus Liguori Page