Y.J. Padmarajiah, A Comparative Study of the Jaina Theories of Reality and Knowledge (Bombay: Jain Sahitya Vikas Mandal, 1963)
An excellent recent work which delves into the origins of anekāntavāda is:
Piotr Balcerowicz, Early Asceticism in Jainism: Ājivikism and Jainism(London: Routledge, 2016)
The following article by John Cort provides a great critique of the frequently asserted claim that anekāntavāda historically functions as a philosophy of 'intellectual ahiṃsā':
John E. Cort, “‘Intellectual Ahimsa’ Revisited: Jain Tolerance and Intolerance of Others” (Philosophy East and West Volume 50, Number 3 July 2000 324-347).
Chapters 5 and 6 of my Jainism: An Introduction (London: IB Tauris, 2009) present, respectively, historical and philosophical analyses of anekāntavāda and the related doctrines, nayavāda and syādvada These analyses, in turn, are based on my 2000 doctoral dissertation from the University of Chicago, Plurality and Relativity: Whitehead, Jainism, and the Reconstruction of Religious Pluralism.
Paul Dundas' The Jains (London: Routledge, 2002–second edition) and Padmanabh S. Jaini's The Jaina Path of Purification (Berkeley: University of California Press, 1979) have relevant sections on anekāntavāda and syādvāda. I also recommend Tara Sethia's 2004 edited volume, Anekānta and Ahiṃsā (Delhi: Motilal Banarsidass, 2004).
This is by no means a complete list, but it is a good start. I hope you find it useful!
With best wishes,
Jeff