His philosophical studies once over, he was chosen by his superiors to represent his community at the Colegio de San Gregorio at Valladolid, an institution of the Dominican Order reserved for extraordinary students.

When Louis had completed these studies, he embarked upon the career of a preacher, in which he continued with extraordinary success during forty years.

His extraordinary sanctity, learning, and wisdom soon attracted the attention of the queen regent, who appointed him her confessor and counselor.

The best known of his ascetical writings, and the one that achieved the greatest measure of success, is The Sinner's Guide (La Guía de Pecadores), published in 1555.

It is marked by a smooth, harmonious style of purest Spanish idiom which has merited for it the reputation of a classic, and by an unctuous eloquence that has made it a perennial source of religious inspiration.

Within a comparatively short time after its first appearance it was translated into Italian, Latin, French, German, Polish, and Greek.

Francis de Sales highly commended to a bishop-elect to have the whole works of Louis of Granada, and to regard them as a second breviary.