True Devotion to Mary is a book by Saint Louis de Montfort on the Roman Catholic theme of devotion to the Blessed Virgin Mary. The book attracted attention in the 20th century when in an address to the Montfortian Fathers, Pope John Paul II said that reading this book had been a decisive turning point in his life.Pope John Paul II (who had a strong Marian devotion) was a follower of de Montfort and singled him out in his Redemptoris Mater encyclical as a key example of Marian devotion.