When I was in seminary in 1966, I discovered in our library a book written by Archbishop Fulton Sheen. He makes simple the truths of our faith. As a priest, I enjoy his works not just for reading, but also for reference.
I recommend:
The Priest Is Not His Own by Fulton Sheen (my favorite)
The Life of Christ by Fulton Sheen
The World's First Love: Mary, the Mother of God by Fulton Sheen