'An Introduction to Yoga' by Annie Besant gives an overview of Yoga, in order to ready the student to take up, for practical purposes, the Yoga sutras of Patanjali, the chief treatise on Yoga. This book leads to the way where tranquility can be attained that can make life peaceful and healthy.

Annie Besant explains the theory of spiritual development based on the teachings of yoga. In the first lecture, 'The Nature of Yoga', Besant talks about consciousness, what is divine, and how they interrelate. The second lecture views the six Indian schools of philosophy, mostly comparing and contrasting yoga to Samkhya and Vedanta-the schools in that yoga is most closely linked. The third lecture views yoga as applied science. Finally, the fourth lecture discusses the practice of yoga. The book also contains some discussion of diet and statements on purifying the physical body.