Introduction To Bhagavad Gita:

Called the royal supreme knowledge rājavidyā rājaguhyaṁ (9.2), this one sacred book conveys the essence of knowledge contained in all written and oral vedic truths to enrich the simplest to complex humans at all planes. It holds within itself the direct key to every possible human enquiry, the solution to every dilemma of emotions, and the sublime righteous path and goal of every quest of rising or falling civilizations for every age, time or geography. As a consequence of the presence of the Gītā, the Mahābhārat epic itself is considered a sacred Hindu scripture.