Schlesinger had intended the book to examine how war-making power had been extended unofficially by the office of the president; in his journal, he reflected that "Watergate came along to provide the climax and, I trust, denouement."

[1] Schlesinger, who had been a vocal advocate for a strong, activist executive being essential to democracy, acknowledges in The Imperial Presidency that expansions of presidential power had led to dangerous abuse of the office.

Schlesinger presents James K. Polk's deployment of troops to the disputed area between Texas and Mexico, leading to the Mexican–American War, as the first example of a president exploiting the ambiguity of war-making powers in the Constitution.

A review in The Baltimore Sun by Stuart Rochester called the book "brilliant, timely", noting that it clearly illustrates Schlesinger's personal conviction of the need for a strong presidency.

[1] Reviewer Richard J. Walton admired Schlesinger's examination of the justification for presidents exceeding the letter of the Constitution, but wrote that the haste with which the book was written was obvious and that some of the language, particularly in regards to Nixon, could be considered overly polemic.

[6] Christopher Lehmann-Haupt observed that The Imperial Presidency read like two overlapping books: one that presents a compelling history of the relationship between the executive and legislative branches of the government, and one that prescribes approaches for dealing with the Watergate crisis.