It is generally mentioned that Bhagavad-gita contains the essence of the knowledge of Vedas and also the preliminary knowledge for the study of spirituality. However when we read Bhagavad-gita we find the main theme is to encourage niskama karma-yoga and also to discourage premature renunciation. This theme recurs in many parts of Bhagavad-gita. So it can be said that Bhagavad-gita is actually a treatise for discouraging premature renunciation and recommending niskama karma-yoga instead, which means the reader should have prior knowledge of these subjects. So can it then really be called a beginners guide to spirituality since it is not actually trying to introduce concepts (although that is done to a small extent), but rather to refute some points and establish others (i.e. don't renounce, fight in Krishna consciousness), which requires prior knowledge of the some of the concepts (e.g. Sannyasa, Karma, Yoga)?