The Abhidhammattha Sangaha is a medieval Buddhist commentary on the part of the Pali Canon called the "abhidhamma," which means something like the distinctly articulated dharma. It was written by Ācariya Anuruddha, about whom literally nothing is known. He must have lived before the 15th century AD when other monks cited him as prolific past author in their own extant texts, but he could have lived in the 6th century or even earlier. It is also unknown what country he is from.
The abhidhamma is quite difficult to understand and the Abhidhammattha Sangaha rearranges into comprehensible categories.
Theravada manuals as enumerated by the Burmese tradition
Abhidhammattha Sangaha | Namarupa-pariccheda | Paramattha-vinicchaya | Abhidhammavatara | Ruparupa-vibhaga | Sacca-sankhepa | Moha-vicchedani | Khema-pakarana | Namacara-dipaka |