Tannishō  歎異抄

A classic text of the Jōdo Shinshū, or ‘True Pure Land school’ of Japanese Buddhism. The title means ‘Notes Lamenting Deviations’, and its contents are said to go back to Jōdo Shinshū founder Shinran (1173-1262), although it is not held to have been composed by him directly. Traditionally, it was compiled by Shinran's great-grandson Kakunyo (1270-1351) from notes taken at Shinran's talks, but internal evidence points to Yuienbō (date unknown), one of Shinran's direct disciples in the Hitachi area. It is thought he may have composed or compiled the work out of concern over misinterpretations of Shinran's teachings. The work is very short, consisting of two parts: ten of Shinran's aphorisms with short commentaries, and eight brief chapters dealing with various misapprehensions of Shinshū doctrine and practice. It is famous as the locus classicus of Shinran's dictum, ‘Even the good person is reborn into Amida's Pure Land; how much more the evil person’, indicating that Amida's grace is directed at the salvation of the more depraved individual. In other passages, Shinran disavows any claims on the part of others that he took personal disciples, and asserts that the nembutsu is itself recited under the grace of Amida Buddha, and cannot be manipulated by the practitioner for worldly or other-worldly gains.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)