Edward Conze 
Buddhist Thought in India [PDF ebook] 
Three Phases of Buddhist Philosophy

Originally published in 1962.This book discusses and interprets the main themes of Buddhist thought in India and is divided into three parts: Archaic Buddhism: Tacit assumptions, the problem of "original Buddhism", the three marks and the perverted views, the five cardinal virtues, the cultivation of the social emotions, Dharma and dharmas, Skandhas, sense-fields and elements. The Sthaviras: the eighteen schools, doctrinal disputes, the unconditioned and the process of salvation, some Abhidharma problems. The Mahayana: doctrines common to all Mahayanists, the Madhyamikas, the Yogacarins, Buddhist logic, the Tantras.