1. J. B. Jackson, the landscape and vernacular historian best known for his The Necessity of Ruins (1980) has written the most influential essay on mobile homes: “The Mobile Home and How It Came to America,” in Discovering the Vernacular Landscape (1984), 91-101 [first published as "The Mobile Home," New Mexico Studies in the Fine Arts, 1982]. Jackson argues that for the entire pre-modern history of architecture two parallel building traditions coincided, one of temporary and permanent architecture. Temporary architecture was built and dismantled within an individual's life time, a tradition that waned in the eighteenth century. Hence, the American trailer is not expedient product of automobiles, but the unique survivor of to a medieval tradition. See Bill's thoughts on this essay here.
2. Two books offer the best historical coverage for campers and trailers. Allan D. Wallis, Wheel Estate: The Rise and Decline of Mobile Homes (1991) is the standard book on camping and campers. John Fraser Hart, Michelle J. Rhodes and John T. Morgan, The Unknown World of the Mobile Home (2002) does not focus on campers on trailer homes. Unlike campers, trailer homes become semi-permanent once they are set into a trailer park. The book contains a number of sociological case studies, including one on Minneapolis (pp. 84-96) and Mercer County, North Dakota (pp. 40-41), based on Caroline S. Tauxe, Farms, Mines, and Main Street: Uneven Development in a Dakota County (1993). It is no surprise that Hart, Rhodes and Morgan dedicate their book to J. B. Jackson.
4. There is a growing focus on mobile architecture from the design field. Postmodern life and concerns over sustainability have caused a boom on portable architecture in design studios throughout the world. There are some wonderful and radical work out there, such as by Atelier Bow Wow (thanks to David Salamon for the cue). In order to get a handle on this creative field, Jennifer Siegel's Mobile: The Art of Portable Architecture (2002) and follow-up More Mobile: Portable Architecture for Today (2008)
5. Finally from the architectural field, the work of Charlie Haylie is important, as it focuses on camps as a new and unique space for our century. His two books are Camps: A Guide to 21st Century Space (2009) and Campsite: Architecture of Duration and Place (2008). Haylie teaches architecture at the University of Florida.