by Thomas G. Bergin. Viking, $25.00. On the reasonable assumption that many readers know nothing about Boccaccio (1313-1375) except that he wrote The Decameron, Professor Bergin offers a short biography of the man and an extensive description of his entire literary output, a body of work that was of enormous importance in the development of European fiction. The book is not light reading but highly informative, since it covers Italian history, contemporary authors, and the beginnings of Renaissance humanism, as well as Boccaccio himself.