The Complete Book of Yoga : Karma Yoga, Bhakti Yoga, Raja Yoga, Jnana Yoga 

The present book describes in detail the philosophy, psychology, and methods of practice in the four yogas. It offers a comparative study of the four yogas, their points of agreement and their differences. Karma-yoga, or the yoga of selfless action, seeks to face the problem of ignorance by eradicating the ego. It is the ego, born of ignorance, that binds us to this world through attachment.