Good introductory discussions of elections and voting can be found in the following books, both of which are written for an undergraduate student audience:
Alan Abramowitz, Voice of the People: Elections and Voting in the United States. (New York: McGraw-Hill, 2004).
William H. Flanigan and Nancy H. Zingale, Political Behavior of the American Electorate, 10th ed. (Washington: CQ Press, 2002).
Considerable historical data on American elections are found in:
Richard G. Niemi and Harold W. Stanley, Vital Statistics on American Politics, 2005-2006 (Washington: CQ Press, 2005).