Brown, Herbert Ross. The Sentimental Novel in America, 1789-1860. Durham: Duke University Press, 1940, 407 p.
Provides both theoretical and critical information about the sentimental novel in general and Cummins in particular.
Cowie, Alexander. “The Vogue of the Domestic Novel, 1850-1870.” South Atlantic Quarterly 4 (October 1942): 416-24.
Investigates the influences and generic stylistic devices of the domestic novel, including references to Cummins's The Lamplighter.
Easson, Angus. “Elizabeth Gaskell, ‘An Incident at Niagara Falls,’ and the Editing of Mabel Vaughan.” English Language Notes 17, no. 4 (June 1980): 273-77.
Discusses Elizabeth Gaskell's editing of Mabel Vaughan—her additions, notes, small deletions—for the London edition published by Samuel Low.
Howard, June. “What is Sentimentality?” American Literary History 11, no. 1 (spring 1999): 62-81.
Provides a theoretical foundation with which to critique Cummins's novels, focusing especially on their adherence to the sentimental genre's anti-Calvinist tradition of elevating the goodness of human nature.
Papashvily, Helen Waite. All the Happy Endings: A Study of the Domestic Novel in America, the Women Who Wrote it, the Women Who Read it, in the Nineteenth Century. New York: Harper, 1956, 231 p.
Comments broadly on the sentimental genre, with numerous references to Cummins throughout.
Additional coverage of Cummins's life and career is contained in the following source published by the Gale Group: Dictionary of Literary Biography, Vol. 42; Literature Resource Center.