Published in 1886, Stevenson's novel sold to Victorians, whose repressive lives lured them to the salacious nature of Mr. Hyde as it is a fact that secretive publications of a sexual nature were distributed widely and prolifically during this era (many women as well as men read forbidden publications secretly). In addition, the notoriety of Charles Darwin's research and his publication of The Descent of Man and the colonization of savage and exotic lands while England was building its empire furthered interest in the primitive side of man as represented by Mr. Hyde.
Stevenson's apparent suggestions in his novel that contemporary Victorians--even a prestigious and well-bred gentleman such as Dr. Jekyll--might yet possess an animalistic side to their beings was intriguing. Thus, The Strange Case of Dr. Jekyll and Mr. Hyde sold over 40,000 copies as people read the musings of Stevenson regarding the divisions of good and evil. After all, London itself had a dual nature, as respectable streets existed in close proximity to areas notorious for their squalor and violence. In fact, during the Victorian age, there were opium dens in East London; one particular one was a famous den run by the Chinaman Ah Sing, which attracted gentlemen from the elite of London’s high society, much like Stevenson's fictional physician.
Addressing the moral question of man's duality, Henry James, brother of the philosopher William James, lauded Stevenson's exploration:
...the subject is endlessly interesting, and rich in all sorts of provocation, and Mr. Stevenson is to be congratulated ... There is a genuine feeling for the perpetual moral question, a fresh sense of the difficulty of being good and the brutishness of being bad.
Notably, other writers and literary critics such as Irving S. Saposnik, point out that Stevenson's fictional paradox of Jekyll/Hyde "revealed the social paradox of London."