Agni Purana is basically a preaching to the sage Vashishth by Agni. In his turn, Vashishth narrated it to Vyasaji, who related it to Sutji. Ultimately, Sutji narrated Agni Purana to an assembly of the sages in Naimisharanya.
Starting chapters of the Purana describe about various incarnations of Lord, including Rama and Krishna. Other chapters describe about religious rituals especially those related to the worship of Lord Shiva. Many chapters have description about the earth, stars and constellations as well as the duties of the kings.
This Purana consists of 9 chapters.