In this remarkable book that includes two works, it is told about ancient Natha tradition which founder was Gorakhnath - great siddha-yogi, who is known as the founder of hatha-yoga. «An Introduction to natha-yoga» contains primary information about occurrence and prevalence of Natha tradition, its representatives - siddha-yogis of past and present. This work confonts the reader with ideology and the doctrine of Natha yogis and gives representation of the basic aspects of practice. "Shiva-tattva" is dedicated to Shiva, in the given text are described his various forms and manifistations and also rituals of worship. The book will be interesting for both skilled sadhakas practising Yoga and Tantra and that who only starts going into Hunduism and various religious currents.