A couple years ago I did a paper on him, so here is the bibliography I had. I will fully admit that many of these sources are distinctly biased toward Makhno but nonetheless they do provide a fair amount of insight.
Let me know if you don't have access to any of the articles and I can send them to you, I still have the PDFs
Adams, Arthur E. "The Awakening of the Ukraine." Slavic Review 22, no. 2 (June 1963): 217-23. ( On JStor )
Arshinov, Peter. The History of the Makhnovist Movement. Translated by Fredy Perlman. Detroit: Black and Red, 1974. ( On Libcom.org )
Avrich, Paul. "Russian Anarchists and the Civil War." Russian Review 27, no. 3 (July 1968): 296-306. ( On JStor )
Footman, David. "Nestor Makhno and the Russian Civil War." History Today 6, no. 12 (December 1956): 811-20. ( On Ebscohost )
_________. Civil War in Russia. New York: Frederick A Praeger, 1962. ( On Libcom.org )
Landis, Erik-C. "Waiting for Makhno: Legitimacy and Context in a Russian Peasant War." Past and Present 183 (May 2004): 199-236. ( On JStor )
Makhno, Nestor Ivanovich. The Struggle Against the State and Other Essays. Edited by Alexandre Skirda. San Francisco: AK Press, 1996. ( On Anarchistlibrary.org )
Malet, Michael. Nestor Makhno in the Russian Civil War. London: London School of Economics and Political Science, 1982. ( On Libcom.org )
Peters, Victor. Nestor Makhno: The Life of an Anarchist. Winnipeg: Echo Books, 1970. ( On Archive.org )
Skirda, Alexandre. Nestor Makhno, Anarchy's Cossack. Translated by Paul Sharkey. Edinburgh: AK Press, 2004. ( This I used a print copy )
Edit: Added links to each of the books
Edit2: Out of curiosity what is your particular interest for?