Light in the Wilderness: Explorations in the Spiritual Life by M. Catherine Thomas.
Cathy and I shared an office for a couple of semesters when she was teaching religion at BYU part-time, and so I know from experience what an amazing woman she is. She taught full time in the religion department at BYU, then retired, has gone on several missions with her husband, and once in awhile returns for a semester to teach part-time. I grew to love her and I cherish all I learned from her. I can't recommend this book highly enough.
Light in the Wilderness is not a quick read. Instead it is a book that you will read paragraph at a time and then ponder. It is beautifully written and packed with insights and encouragement on gospel living and how to draw closer to Jesus Christ.