Raja Yoga is the King of all Yogas. It concerns directly with the mind. In this Yoga there is no struggling with Prana or physical body. There are no Hatha Yogic Kriyas. The Yogi sits at ease,watches his mind and silnces the bubbling thoughts. He stills the mind and restrains the thought waves, enters into the thoughtless state of Asamprajnata Samadhi. Hence the name Raja Yoga. Though Raja Yoga is a dualisitic philosophy and treats of Prakriti and Purusha,it helps the student in Advaitic realisation of openness eventually. Though there is the mention of Purusha,ultimately the Purusha becomes identical with the highest Self or Brahman of the Upabnishads. Raja Yoga pushes the student to the highest ring of the spiritualm ladder,Advaitic realisation of brahman.
Like many other books of the author this book also has run into many editions since it's first publication in the year 1937.