Abhidhammattha Sangaha is a highly popular primer, or digest, of the Abhidhamma corpus (the scholastic section of the canon) of the Theravada tradition. The Abhidhammattha-sangaha was composed in India or in Myanmar (Burma), the chief centre for Abhidhamma studies. Written in Pali by the monk Anuruddha, it dates from no earlier than the 8th century and probably from the 11th or 12th. An outline of the text is here: A Comprehensive Manual of Abhidhamma