Reddit reviews THE IMITATION OF CHRIST

You must be incorporated into the Body of Christ, His Church. This happens either through baptism or formal reception of baptized individuals (usually RCIA). [ccc 1267]

Here is some good reading material:

All Things Made New: The Mysteries of the World in Christ by
Stratford Caldecott

The Seven Sacraments: Entering the Mysteries of God by Stratford Caldecott

Introduction to Christianity by Pope Benedict XVI (any theology by the Pope Emeritus)

New Seeds of Contemplation by Thomas Merton

The Spirit of Early Christian Thought: Seeking the Face of God by
Robert Louis Wilken

Fundamentals of Catholic Dogma by Ludwig Ott (best to get this from a library).

Apologia Pro Vita Sua by John Henry Cardinal Newman

The Spanish Mystics: The Way of Perfection and The Interior Castle by St. Teresa of Avila, The Dark Night of the Soul, The Spiritual Canticle and The Ascent of Mt. Carmel by St. John of the Cross, The Spiritual Exercises by St. Ignatius of Loyola, The Mystical City of God by Maria de Jesus de Agreda

St. Louis-Marie de Montfort: True Devotion to Mary, The Secret of Mary, The Secret of the Rosary

The Imitation of Christ by Thomas a Kempis

The Cloud of Unknowing (an anonymous work)

Note that the older works are all free online, I linked to amazon for convenience. I'll come back if I remember more.