St. Teresa of Avila (Wikipedia), a reformer of the Carmelite Order, is one of the most important authorities on the Spiritual Life. She is a "Doctor of the Church" and I HIGHLY recommend you read or listen to her writings...
When I was a Novice with the Capuchin Franciscans, the following books were assigned as required reading. Thomas Green, SJ has a wonderful way of bringing the Spirituality of St. Teresa of Avila and St. John of the Cross to an easier level of understanding. These are EXCELLENT...