Answer
It is a conversation between Ashtavakra and Maharaja Janaka, the father of Sita Devi and the father-in-law of Lord Rama. Of course, it is transcendental literature, but it mainly discusses the impersonal aspect of the Absolute Truth.
The Bhagavad-gita, however, directly explains the personal feature of the Absolute Truth, which is the highest understanding of the Absolute. The impersonal aspect of the Absolute Truth is only the beginning stage of realization, known as the Brahman feature. Above that is the Paramatma feature — the Supersoul situated in the heart of every living being. The topmost realization of the Absolute Truth is the realization of the Personality of Godhead, Lord Krishna or Vishnu.
Therefore, if someone is interested in the ultimate perfection of self-realization, God realization, or realization of the Absolute Truth, they must engage in devotional service. The Bhagavad-gita describes various spiritual processes, but because it is spoken directly by Bhagavan Sri Krishna, it especially emphasizes bhakti. Krishna explains that the bhakti-yogi is the topmost yogi, and devotional service is the supreme process for attaining the highest realization of God
