Below are the authoritative sources of Catholic Truth. As much as possible, the content on this website follows these sources.
The Institutes Online or Print
The Conferences Online or Print
The Ladder of Divine Ascent Online or Print
Imitation of Christ Online or Print
Introduction to the Devout Life Online or Print
The Spiritual Combat Online or Print
The Secret of the Rosary Online or Print
True Devotion to Mary Online or Print and Consecration guide
The Holy Fathers
Summary of Catholic Doctrine with links to the Summa
List and definition of all virtues from Thomist Philosopher Fr. Ripperger
Glossary of Philosophical Terms
Free iPieta App– excellent mobile app with numerous Authoritative sources
Non-Authoritative but recommended books
The Current Crisis
Iota Unum: A Study of Changes in the Catholic Church in the 20th Century by Romano Amerio – this classic text is a must read.
The Devastated Vineyard by Dietrich von Hildebrand online or print – another classic written in 1973 by one of the great men of the 20th century.
The Charitable Anathema by Dietrich von Hildebrand – a collection of essays on the crisis before his death in 1977.
Infiltration by Dr. Taylor Marshall – best historical introduction to this crisis in print. My defense of this work here.
Topics on Tradition by Fr. Chad Ripperger – diagnosing the breakdown of doctrine
Magisterial Authority by Fr. Chad Ripperger – concise clarity on Magisterial truth and error
The Binding Force of Tradition by Fr. Chad Ripperger – concise clarity on truth and error on Tradition
The Greek Schism
Russia and the Universal Church – Vladimir Soloviev’s seminal work unmasking the Greek schism Online or Print
The Early Papacy: To the Synod of Chalcedon in 451 by Adrian Fortescue – an excellent introduction to the history of the Papacy
I have researched the copyright law regarding these works published before 1978 and reprinted by various publishers. Many of them have been obtained via archive.org. It appears that these works are in the public domain, but if I have made an error in this please contact me.
 The New Catechism of St. John Paul II is not authoritative in every statement because it includes instances of Sententia Communis and Probabilis without making such distinctions. Thus a new reader would not be able to use this as completely authoritative. An example is the inclusion of the teaching that Muhammadans and Christians worship the same God and the prudential condemnation of the death penalty. Both of these matters are under dispute and are not part of the faith (the Holy Office explicitly declared, for example, that faithful Catholics are permitted to disagree with the Pope on the death penalty in 2004). It is recommended that the reader first read the older catechisms in order to properly benefit from the new.