This is an initial list of some of the books that I have found most useful in learning about Indian music
Sandeep Bagchi, Nād: Understanding Indian Music; Mumbai, Eeshwar, 1998. One of the best and clearest introductions to Hindustani music, winsomely illustrated with old drawings.
Janaki Bakhle, Two Men and Music: Nationalism in the Making of an Indian Classical Tradition; Oxford, Oxford University Press, 2005. A profoundly engaging study of two Vishnus: Vishnu Narayan Bhatkhande (1860-1936) and Vishnu Digambar Paluskar (1872-1931).
Vishnu Narayan Bhatkhande, Hindustānī sangīta-paddhati kramika pustaka-mālikā. 1968, Hathras, Sangit Karyalay, 1954-68. A six-volume treasury of song compositions with sargam and tala notation.
Joep Bor, et al., The Raga Guide: a Survey of 74 Hindustani Ragas; Rotterdam, Nimbus Records, 1999. A highly useful guide: brief, two-page introductions to each raga with brief sung or played examples on a series of six CDs.
A.H. Fox Strangways, The Music of Hindostan; Oxford, The Clarendon Press, 1914. Both dated and timeless.
Nazir Ali Jairazbhoy, The Rāgs of North Indian Music: their Structure and Evolution; Middletown, Wesleyan University Press, 1971. (There is also a later Indian edition.) Almost encyclopaedic information; accessibly written, with musical examples in sargam as well as staff notation.
James Kippen, The Tabla of Lucknow: a Cultural Analysis of a Musical Tradition; Cambridge, Cambridge University Press, 1988. See my informal review here.
T.M. Krishna, A Southern Music: the Karnatik Story; Noida, HarperCollins, 2013. TMK’s new, exciting, wide-ranging meditation on Carnatic music from a myriad different perspectives. Inspirational. Find him on Youtube also.
Nicolas Magriel with Lalita du Perron, The Songs of Khayāl. 2 vols & CD. Delhi, Manohar, 2013. A wonderful resource: a detailed study of khayāl with transcriptions of the words and music of classic performances. Reviewed here.
Peter Allen Roda, ‘Resounding Objects: Musical Materialities and the Making of Banarasi Tablas'. New York University, PhD Dissertation, 2013. A wonderfully detailed and ethnographically rich piece of research. Publishers, please publish!
Sangirangi. Not a book but an entirely wonderful website that constitutes the life-work of sarangi scholar and player Nicolas Magriel: an astonishing collection of recordings and information about the sarangi and its tradition in present-day India.
Ravi Shankar, Raga mala : the Autobiography of Ravi Shankar, ed. George Harrison; Guildford, Genesis Pub. Ltd., c.1997. Especially good on Panditji’s tutelage under his brother, the dancer Uday Shankar, and their early experiences in Paris and elsewhere.