Critics praised the writing style and depth of research, but described the scope as exceptionally broad, limiting the work's ability to cover individual subjects.

The early chapters focus on an array of figures in eighteenth- and nineteenth-century American religious movements, such as Ann Lee, Henry Steel Olcott, Helena Blavatsky, Joseph Smith, and the Public Universal Friend.

Horowitz covers the origins of the Ouija board in the mid-nineteenth century; its later commercialization by William Fuld, a Presbyterian businessman who openly disclaimed the object's supernaturalism; and its influence on popular culture, such as its inspiration of the Pulitzer-winning epic poem The Changing Light at Sandover.

Occult America's eighth chapter deals with the role of esotericism in twentieth-century politics, particularly through Franklin D. Roosevelt's vice president Henry A. Wallace.

By discussing supernatural or esoteric beliefs openly, practitioners in the United States brought such ideas into the mainstream, inspiring the twentieth-century popularity of phenomena such as astrology and numerology.

Bowman was similarly disappointed by Horowitz's relatively brief description of Mormonism, which he felt was unduly focused on by the book's blurb, but referred to Occult America's ability to cover figures as diverse as Joseph Smith, Mary Baker Eddy, and Maharishi Mahesh Yogi as "an achievement not to be sneezed at".

[12] Eugene Taylor, writing from a Swedenborgian perspective, felt Occult America underrepresented Emanuel Swedenborg's influence on American religious history; nonetheless, he called the book "a fascinating subject and a great read" but inclined to "ignore or downplay the dark side of the movement [Horowitz] is describing".

[13] Bowman identified the book's definition as "anything Horowitz finds novel, interesting, or appropriately weird", criticising it as imprecise and arguably applicable to mainstream religions such as Orthodox Judaism.

[12] Occult America was a winner of the 2010 PEN Oakland Josephine Miles Award, alongside Anna In-Between by Elizabeth Nunez and Master of the Eclipse by Etel Adnan.