“Less popular” as in: not Pride and Prejudice or anything by Dumas.
I was looking at my stats on Goodreads and discovered that it’s been seven years since I read Eugene Onegin by Pushkin. Since then I’ve read some books written in the late 19th century, but nothing before 1850.
I definitely recommend Pushkin. He wrote poetry but it’s very accessible.
I read Wilkie Collins 1868 (which I know is later than you asked but it’s set 1846-48) novel No Name.
I read it because I was intrigued by the title and premise, it’s a revenge plot but the person getting revenge is an 18 year old woman seeking vengeance/justice after she and her sister are left with nothing after their parents sudden deaths, due to their parents not being married when they were born, a fact hidden from them their entire lives.
It suffers from a few plot conveniences that I don’t love and the last two chapters are meh, but the plot was very engaging and the main character, Magdalen Vanstone, is quite different from other Victorian and earlier heroines.