Jennings is also an
amusement park historian. In August 2009, his first book, ''
Knott's Berry Farm: The Early Years'', was published by
Arcadia Publishing and features over 200 rare photographs that haven't been widely circulated. The book goes into great detail in describing the history of Knott's Berry Farm and its founder,
Walter Knott, including chapters about the park's Ghost Town, its attractions, street performers, and shops. As of 2006, Jennings has been curator of ''The Knott's Berry Farm Museum'', home to the largest collection of
vintage Knott's
memorabilia in the world. A copy of his book is housed in the
Library of Congress. In August 2012, Jennings' second book, ''Beverly Park: L.A.'s Kiddieland, 1943-74'', was published by Retro Image Publishing and features 175 never-before-published photographs. The book tells the story of
Beverly Park (also known as 'Kiddieland') and its owner Dave Bradley, who was a ride inventor and pioneer in the amusement park industry. There are also chapters dedicated to all the
kiddie rides, attractions, grounds, and party areas that made the park so popular for over 30 years. Beverly Ponyland, a place where children rode
ponies around a track for 34 years and was located down the street from Beverly Park, is also covered in the book. In January 2019, Jennings' third book, ''Bob McAllister's Wonderama'', was published, which chronicles the history of the popular, children's TV show from the 1960s and 70s. ==Works==