The Oxford Handbook of the American Presidency. New York, Oxford University Press, 1989. 877 pp. Sections include: Approaches to studying the presidency, the legislative presidency, foreign relations, decision making, implementing policy. 35 chapters each about 20 pp. written by political scientists. The benefit of books like this and the Oxford Bibliographies is that they do the legwork for you; that is, they tell you what the best sources are.
http://oxfordbibliographies.com/obo/page/political-science. Latest update June 2017. Annotated bibliographies compiled by experts in the field. Sections on the presidency: Presidential Persuasion and Political Opinion;Presidential Primaries and Caucuses; Public Presidency, U.S. Elections, and the Permanent Campaign; US Presidency. Students should familiarize themselves with the contents of the last section which is an overview of all major writings on the presidency.
The Presidency A to Z. 5th ed. Thousand Oaks, CA: CQ Press, 2013. 715 pp.
Sayler, James. Presidents of the United States--Their Written Measure: a Bibliography. Washington, D.C.: The Library of Congress, 1996. The first part is a general bibliography on the presidents, the second covers the writing of and about the presidents up to Clinton. Though dated very valuable since it based on the Library of Congress collection.
Kane, Joseph Nathan and Janet Podell. Facts About the Presidents. 8th ed. New York: H.W. Wilson, 2009. Van Pelt Reference E 176.1.K3 2009 Part 1 is a chronological listing with details about each administration uniformly arranged covering areas such as cabinet officials, family members, military experience. Part 2 is more statistical and focuses on elections and legal matters.