"The Power of Now" is a spiritual guide written by Eckhart Tolle that emphasizes the importance of living in the present moment. Tolle argues that many people are trapped in their thoughts about the past or future, which leads to anxiety and unhappiness. By focusing on the now, individuals can experience a deeper sense of peace and fulfillment. The book encourages readers to observe their thoughts without judgment and to cultivate mindfulness. Tolle introduces concepts such as the ego and the pain-body, which represent the mental patterns that hinder personal growth. Through awareness and acceptance, readers can transform their lives and achieve inner tranquility.