Hello! A few years ago we beefed up the library at Bhavana Society, based on an annotated bibliography of Mu Soeng. The following represents a consensus of Bhante Gunaratana and Mu Soeng on the essential scholarship about Buddhism in India. My personal favorites on this list are Auboyer, Gethin, Hamilton, Hirakawa & Groner, Nakamura, Strong, and of course Warder. I hope this helps.
Ahir, D.C. Buddhism in South India. Delhi: Sri Satguru Publications, 1992.
Auboyer, Jeannine. Daily Life in Ancient India from 200 bc to 700 ad. London: Phoenix Press, 1965, 2002.
Bagchi, Jhunu. The History and Culture of the Palas of Bengal and Bihar: (Cir. 750 A.D. - Cir. 1200 A.D.). New Delhi: Abhinav, 1993.
Basham, A.L. The Wonder That Was India New York: Grove Press, 1954.
Bhattacharyya, Narendra Nath. Buddhism in the History of Indian Ideas. New Delhi: Manohar, 1993, 2000.
Bronkhorst, Johannes. The Two Traditions of Meditation in Ancient India Delhi: Motilal Banarsidass, 1993, 2000.
Bu-ston, Rin-chen-grub. The History of Buddhism in India and Tibet Trans. E. Obermiller. Bibliotheca Indo-Buddhica ; No. 26. 2nd ed. Delhi: Sri Satguru Publications, 1986, 1999. First published: Heidelberg, 1932.
Chakravarti, Uma. The Social Dimensions of Early Buddhism. Delhi: Oxford University Press, 1987.
Chinchore, Mangala R. Anatta/Anatmata, an Analysis of Buddhist Anti-Substantialist Crusade. Bibliotheca Indo-Buddhica Series ; No. 158. 1st ed. Delhi: Sri Satguru Publications, 1995.
Collins, Steven. Nirvana and Other Buddhist Felicities: Utopias of the Pali Imaginaire. Cambridge Studies in Religious Traditions ; 12. Cambridge: Cambridge University Press, 1997.
Conze, Edward. Buddhist Thought in India. Ann Arbor: Ann Arbor Paperbacks, 1962, 1967.
Dutt, Nalinaksha. Early Monastic Buddhism. 2d ed. Calcutta: Firma K. L. Mukhopadhyay, 1971, 1980.
---. Buddhist Sects in India. 2nd ed. Calcutta: Firma K. L. Mukhopadhyay, 1978, 1988.
Dutt, Sukumar. Buddhist Monks and Monasteries of India: Their History and Their Contribution to Indian Culture. Delhi: Motilal Banarsidass, 1962, 1988.
Dutt, Sukumar. Early Buddhist Monachism. 1924. 2nd ed. New Delhi: Munshiram Manoharlal, 1996.
Ergardt, J.T. Man and His Destiny: The Release of the Human Mind: Study of Citta in Relation to Dhamma in Some Ancient Indian Texts. Leiden: E. J. Brill, 1986.
Gethin, R. M. L. The Buddhist Path to Awakening: A Study of the Bodhi-Pakkhiya Dhamma. Oxford: Oneworld Publications, 2001. Previously published by E.J. Brill, 1992.
Gombrich, Richard F. How Buddhism Began: The Conditioned Genesis of the Early Teachings. New Delhi: Munshiram Manoharlal Publishers, 1997, 2002.
Hamilton, Sue. Identity and Experience. The Constitution of the Human Being According to Early Buddhism. London, 1996.
Hamilton, Sue. Early Buddhism: A New Approach: The I of the Beholder. Curzon, 2000.
Hardy, R. Spence. Eastern Monachism. 1850, Partridge and Oakey, London. Delhi: Sri Satguru Publications, 1989 .
Hazra, Kanai Lal. Royal Patronage of Buddhism in Ancient India. Delhi: D.K. Publications, 1984.
---. The Rise and Decline of Buddhism in India. New Delhi: Munshiram Manoharlal Publishers, 1995.
Hirakawa, Akira, and Paul Groner. A History of Indian Buddhism: From Sakyamuni to Early Mahayana. Asian Studies at Hawaii ; No. 36. Honolulu: University of Hawaii Press, 1990.
I ching. A Record of the Buddhist Religion as Practiced in India and the Malay Archipelago. First published by Clarendon Press, London. 1896. Trans. Junjiro Takakusu. Delhi: Munshiram Manoharlal, 1966.
Joshi, Lal Mani. Studies in the Buddhistic Culture of India: 7th and 8th Centuries A.D. Delhi: Motilal Banarsidass, 1967.
Kimura, Ryukan. The Original and Developed Doctrines of Indian Buddhism in Charts. Delhi: Pilgrims Book Pvt. Ltd., 1920, 1998.
Lamotte, Etienne. History of Indian Buddhism: From the Origins to the Saka Era. Publications De L'institut Orientaliste De Louvain, 36. Louvain-la-Neuve: Université catholique de Louvain, Institut orientaliste, 1988.
Law, Bimala Churn. Geography of Early Buddhism. Originally published by K. Paul, Trench, Trubner, London. 1932. Varanasi: Bhartiya Pub. House, 1973.
Legge, James. A Record of Buddhistic Kingdoms: Being an Account by the Chinese Monk Fa-Hien of His Travels in India and Ceylon A.D. 399-414. Translated and Annotated. New York: Paragon Books, 1965.
Mookerji, Radha Kumud. Asoka. Delhi: Motilal Banarsidass, 1928.
Nakamura, Hajime. Indian Buddhism: A Survey with Bibliographical Notes. Delhi: Motilal Banarsidass, 1987 , 1999.
Nikam, N.A., and Richard McKeon. The Edicts of Asoka. Chicago: University of Chicago Press, 1959.
Oldenberg, Hermann. The Doctrine of the Upanisads and the Early Buddhism. Trans. Shridhar B. Shrotri. 1st ed. Delhi: Motilal Banarsidass Publishers, 1991.
Pande, Govinda Chandra. Studies in the Origins of Buddhism. Delhi: Motilal Banarsidass, 1995, 1999.
Parrinder, Geoffrey. The Wisdom of the Early Buddhists. New York: New Directions, 1977.
Ratnapala, Nandasena. Buddhist Sociology. Delhi: Sri Satguru Publications, 1995.
Rhys Davids, T.W. Buddhist India. Delhi: Motilal Banarsidass, 1971.
Sankrityayan , Rahula, et al. Buddhism: The Marxist Approach. Delhi: People's Pub. House, 1970.
Schober, Juliane, ed. Sacred Biography in the Buddhist Traditions of South and Southeast Asia. Honolulu: University of Hawaii Press, 1997.
Sircar, Dineschandra, and Asoka. Inscriptions of Asoka. 3d ed. New Delhi: Publications Division, Ministry of Information and Broadcasting, Govt. of India, 1975.
Strong, John. The Legend of King Asoka: A Study and Translation of the Asokavadana. Princeton: Princeton University Press, 1983.
Strong, John. The Legend and Cult of Upagupta: Sanskrit Buddhism in North India and Southeast Asia. New Delhi: Motilal Banarsidass, 1994.
Taranatha. Taranatha’s History of Buddhism in India. Trans. Lama Chimpa and Alaka Chattopadhyaya. Delhi: Motilal Banarsidass, 1970, 1997.
Upreti, G.B. The Early Buddhist World Outlook in Historical Perspective. New Delhi: Manohar Publishers and Distributors, 1997.
Varma, Vishwanath Prasad. Early Buddhism and Its Origins. 1st ed. New Delhi: Munshiram Manoharlal Publishers, 1973.
Wagle, N. K. Society at the Time of the Buddha. 2nd rev. ed. Bombay: Popular Prakashan, 1995.
Warder, A.K. Indian Buddhism. Delhi: Motilal Banarsidass, 1970, 1980.
Wijesekera, Oliver Hector de Alwis. Buddhist and Vedic Studies: A Miscellany. 1st ed. Delhi: Motilal Banarsidass Publishers, 1994.