Holy Confidence; or Simplicity with God is a religious book by Benedetto Rogacci that explores how a life of simplicity can lead to a deeper relationship with God, emphasizing faith, prayer, and trust. It encourages readers to focus on their spiritual lives, let go of worldly distractions, and practice humility and virtue to strengthen their faith. The book, which is a translation from the Latin work 'Unum Necessarium', offers a guide for achieving a more meaningful spiritual life by cultivating confidence in God's plan.