Wilkie Collins 
The Evil Genius: A Domestic Story [PDF ebook] 

Wilkie Collins is best known as a writer of sensationalist fiction: supernatural suspense, terrifying drama, complex mysteries, and all often used as a vehicle for his complaints against social injustices. The Evil Genius doesn't fall into that category by today's standards, but for Victorians, it's very subject matter was sensational and taboo. The Evil Genius is novel of marital infidelity, Divorce (yes, with a capital "D"!) and the scandal and injustice that often (in Collins' times) surrounds these issues.
Sydney, a young governess raised without parents to guide her in correct ways, finds her gratitude for her employer gradually slide into infatuation. Mr. Linley (the employer), finds his enchantment of Sydney returned by her infatuation, and an indiscretion is made and immediately regretted. Sydney loves Mrs. Catherine Linley, and considers her a dear friend, and she loves her pupil, Kitty with deep affection. They agree that Sydney must leave and Linley will confess all to Catherine. Catherine forgives, Sydney leaves for another position, and all would have returned to normal except that Kitty became grievously ill and wouldn't rest until she could see her dear Syd again. Accidentally alone, Sydney and Linley renew their forbidden love and are witnessed by Catherine. This time she can not forgive, and she banishes them both.
What follows in the meat of the novel is a, not always under the surface, discussion of the unfairness of the law and society toward women in this situation. For example, as long as they are married, Linley only is the guardian of the child, by law. Only if a Divorce occurs does legal parental guardianship go to the mother. One character, Catherine's lawyer, expresses hope that the future may see a change in this law.
When it is discovered by the residents of a small seaside resort that Catherine is Divorced, despite the fact it was her husband's infidelity, she and her daughter are shunned. Dear friends that are (as Collins puts it) "deeply religious", see any potential remarriage as a sin, in spite of the fact that (again, as Collins notes) the very verse they are quoting follows a verse that presumes the Divorced woman to have been the unfaithful one.
Collins is really stepping out of the Victorian mores and making some controversial statements with this novel, and yet it doesn't read like a morality tale. The prose is excellent and the point of view shifts gently, sometimes so subtly as to be nearly undetectable, between main characters and causes the reader to change views of the characters as the point of view shifts. While melodramatic by today's standards, the story is still tense and interesting.