What is the relationship between Charlotte Bronte's Jane Eyre and her next novel, Shirley?

There are a few similarities between Charlotte Bronte's Shirley and her novel Jane Eyre. For one thing, there is no doubt that Shirley is a continuation of the discourse on women by Brontë that began with her previous novel.
Victorian novels
Both novels are classified as Victorian narratives that critique certain aspects of Victorian society and the historical setting. The two novels both fall under the category of the popular “public” novel, as there are characters of various social classes and the narrative informs the reader about the society of the time.Certainly, industrialization is a part of the focus of Shirley but not a concern in Jane Eyre. Nevertheless, the narrative of Brontë's next novel also involves its plot with class consciousness and the role of women in society, as does Jane Eyre. Not unlike Jane, Caroline, who is also an orphan, secretly loves a man who is in a higher socio-economic class than she is. Caroline also has an identity crisis, but after she falls ill from being heart-sick and weak, her long-lost mother appears. As she is reunited with her natural mother, Caroline is given a reason to live and recovers. Similarly, Jane Eyre finds her relatives, St. John Rivers and his sisters, and is reunited with Mr. Rochester.
The "Woman Question"
Perhaps the strongest relationship between the two books is that of the "Woman Question"; that is, women's roles and their legal status. This "question" involves women's roles in society and how they are regarded. Not unlike Jane Eyre, Shirley Keeldar is an independent and strong-willed woman, although she is able to achieve more because of her social position as an heiress. Nevertheless, Jane Eyre, like Shirley, is able to choose whom she loves and marries. Thus, both women find self-fulfillment in marriage.
http://www.victorianweb.org/authors/bronte/cbronte/diniejko.html