The second essential book is Catechism, the compendium of the faith of the Catholic Church. The structure of this book concentrates almost all the important topics for Catholics in short readings. For an even more condensed version, you can read the abridged compendium of the Catechism.
4. Enjoy a good read
There are also many other books that guide the spiritual life of a Catholic, including Caminoby Saint Josemaría Escrivá de Balaguer; Towards a philosophy of Christian educationby Saint John Paul II; Confessions of San Agustín, Los Spiritual exercises of San Ignacio de Loyola; e Imitation of Christ by Thomas of Kempis.
The latter, written more than 500 years ago, is considered the second most read book after the Bible. The work is composed of four books, where the author traces the progress of the soul up to and including its union with God in Holy Communion.