Wright, H. Nelson, Coins of the Mughal Emperors, Formerly published as Catalogue of the Coins in the Indian Museum, Calcutta, Vol. III, Mughal Emperors of India, Calcutta, 1908. Reprinted by Deep Publications, Delhi, 1975. One of the main references on the Mughal Emperors. A good historical introduction. Not quite as user-friendly as the BMC catalogue, but good nonetheless. A fair number of coins photographed, ex The Skanda Collection Library.
Estimate: 15-25 USD