Herewith a very selected list of some of the books I found most helpful in understanding the legal and historical background of the Heller case and the history and practice of gun regulation in America. Not listed, but probably most important, are all the briefs filed in the case itself, which themselves give a full education on all the subjects and controversies surrounding the Second Amendment. They are all available at http://www.dcguncase.com/blog/casefilings/.
Cramer, Clayton E. Armed America: The Story of How and Why Guns Became as American as Apple Pie. Nashville: Nelson Current, 2006.
Davidson, Osha Gray. Under Fire: The NRA and the Battle for Gun Control. New York: Henry Holt, 1993.
Halbrook, Stephen P. That Every Man Be Armed: The Evolution of a Constitutional Right. Oakland, CA: Independent Institute, 1994.
Kleck, Gary, and Don B. Kates. Armed: New Perspectives on Gun Control. Amherst, NY: Prometheus Books, 2001.
Kopel, David, Stephen P. Halbrook, and Alan Korwin. Supreme Court Gun Cases: Two Centuries of Gun Rights Revealed. Phoenix: Bloomfield Press, 2004.
Malcolm, Joyce. To Keep and Bear Arms: The Origins of an Anglo-American Right. Cambridge, MA: Harvard University Press, 1994.
McClurg, Andrew J., David B. Kopel, and Brannon P. Denning, eds. Gun Control and Gun Rights: A Reader and Guide. New York: New York University Press, 2002.
Nisbet, Lee, ed. The Gun Control Debate, 2nd ed. Amherst, NY: Prometheus Books, 2001.
Snyder, Jeff. Nation of Cowards: Essays on the Ethics of Gun Control. St. Louis, MO: Accurate Press, 2001.
Vizzard, William J. Shots in the Dark: The Policy, Politics, and Symbolism of Gun Control. Lanham, MD: Rowman & Littlefield, 2000.
Williams, David C. The Mythic Meanings of the Second Amendment: Taming Political Violence in a Constitutional Republic. New Haven, CT: Yale University Press, 2003.
Young, David E., ed. The Origin of the Second Amendment: A Documentary History of the Bill of Rights, 1787–1792, 2nd ed. Ontonagon, MI: Golden Oak Books, 1995.