There are indeed examples of Victorian reactions to Robert Louis Stevenson’s The Strange Case of Dr. Jekyll and Mr. Hyde. Shortly after the novella was written, reviews began to appear in newspapers. Many thousands of copies of the novella were sold during its author's lifetime, which alone is evidence of its popularity during this period. Its at-the-time sales may have been bolstered by the excitement shown in the novella's reviews.
One 1886 reviewer, Andrew Lang, praised Stevenson for his treatment of the idea of double personalities (good and evil) existing within a single person because Stevenson’s execution of the idea was unique compared to previous authors who had used a similar concept (Lang’s review provided by The British Library).
Another reviewer anonymously wrote of Stevenson’s genius in creating such an intricate piece, saying that it is a work that goes deeper than similarly dark stories by Edgar Allan Poe and that readers would certainly need to read it twice (Anonymous review provided by The British Library).
If you need to find exact quotes, digital scans of these reviews are available in the online collection of The British Library at the links below.