It was spoken by Shukadeva Goswami, the son of Vyasadeva – the compiler of all the Vedic literature, to King Parikshit on the banks of the Ganges, when the latter was cursed to die after seven days. It is composed of eighteen thousand verses divided into 12 cantos. The Bhagavad gita, which consists of 700 verses, is considered the essence of all the Upanishads. These two books, namely the Bhagavad gita and the Bhagavatam are enough to gain a complete insight of the Supreme Absolute Truth.
Just as the Ganga is considered the best among the rivers, Krishna – the most exalted among all deities and Lord Shiva as the best among the devotees of Krishna, similarly the Bhagavatam is considered the best among all the Puranas. It is the natural commentary of the Vedanta Sutra since it is written by the author, Vyasadeva himself.