by Charlotte Brontë
Shirley was the middle of the three novels that Charlotte Brontë bequeathed to us, Jane Eyre and Villete (published in 1853.) Charlotte Brontë is particularly interesting for her intellectual network (1) Even though Charlotte Brontë grew up in an isolated social environment, as the most succesful (and long lived) of the Brontë sisters, Charlotte Brontë "got out." She benefited from extensive reviews of her published works, and cultivated a network of similar minded Artists and professionals.
The most basic of these people was Elizabeth Gaskell, who is herself a well remembered Author. Gaskell wrote a "best selling" biography of Charlotte Brontë in 1857, that surely increased the Audience for Charlotte Brontë. It is easy to see Brontë crushing Jane Austen in terms of Audience size between 1800 and 1860.
Charlotte Bronte actually hung out with William Makepeace Thackeray, author of Vanity Fair, and it is fair to say that she was inspired by Vanity Fair (published in 1848) in the same way a band would be influenced by another band. Barry Lyndon was another Thackeray classic that didn't make Boxalls 1001 Books To Read Before You Die list
But ultimately the Bronte sisters must give way to Charles Dickens turning out arguably his greatest work, David Copperfield, in 1850, followed by the less appreciated at the time but more significant in terms of it's artistic influence, Moby Dick. The first of those books is the apotheosis of pre-modern era of the Novel, the second is the firing the gun of the modern period, when the Novel became more serious and important in the eyes of Artistis and Audience.
If you compare the popularity of Jane Austen, Charlotte Bronte and Herman Melville from the 19th century through the 21st, it is easy to see that Jane Austen has retained the most relevance, but Melville and Bronte are both respectably behind her. You can see in the Google Ngram that there was actually a period where Melville drew close to Austen, nipping at her heels- between 1954 and 1959. During that same five year period, Bronte was at her lowest point, whereas more recently she actually surpassed Melville in popularity.
Hard to see the fan base for this particular novel outside of literature under graduate and graduate students, since everyone in the world would read Jane Eyre first and Shirley never.
(1) In The Sociology of Philosophies: A Global Theory of Intellectual Change, Randall Collins describes intellectual networks of philosophers throughout history. Closer to the modern period, those philosophical networks include people who wrote Novels and published other works of literature, making the novel one of the elements of his philosophical networks.
To give an example of Authors who are placed in Collins intellectual networks, as described in Sociology of Philosophies, you have Alexander Pope, Jean-Jacques Rousseau and Charles Dickens to name three. In a particularly intensive piece of writing about literature in the 18th century, Collins runs through an analysis of Dostoyevsky, Franz Kafka, Albert Camus, Sir Walter Scott, Honore Balzac.
Collins makes some adept observations about the markets for Art,
"An elite can survive only with external financial support. Occasionally this happens by bootlegging avant-garde material into works for the middlebrow market; this is one reason for the adulation of Dostoyesvky, who unconsciously carried off this fusion by making his topic the rebellious Russian intellectuals of his day. Similarly, the admiration of French intellectuals went to Hemingway, for his amalgamation of adventure story, stylistic severity and quasi-metaphysical code of meaning." @ PG 774