[Bhagavat Gita was not written as seperate Book. In Mahabaratha it has been quoted in Bheeshma Parva between 25th to 42 Athyaya ]
Bhagavad Gita means the meanings of upanishads told by Lord Krishna to Arjuna in the battle field of Gurukshetra. You have to follow the transcendental knowledge of the most profound spiritual nature as revealed in the Bhagavad- Gita. It is the divine discourse spoken by the Supreme Lord Krishna Himself and is the most popular and well known of all the sacred scriptures from ancient India. Always being revered as a true source of spiritual knowledge it reveals the purpose and goal of human existence. In conjunction to this we will be presenting precise Vedic verification of the Supreme Lord Krishna's divine incarnations as evidence confirming His supreme position. Thro Bhagavad- Gita We want our readers to follow the guidance of Lord Krishna in their Normal Life and to get his blessings by way of doing the Dharma, Good Talking , and to the leave the worldly pleasures, in human life.

You can follow the link at http://www.bhagavad-gita.org/ wherein you can learn a lot of
things from Bhagavad Gita.