Saint Catherine of Siena: The Story of the Girl Who Saw Saints in the Sky
Saint Louis de Montfort: The Story of Our Lady's Slave
Mary Fabyan Windeatt
Though written for children 12 and older, this is also the best biography for adults of St. Louis De Montfort, the "Apostle of Mary," famous preacher and author of True Devotion to Mary and The Secret of the Rosary. Truly inspiring!