Appearances figure in the novel both figuratively and literally. Dr. Jekyll definitely wants to keep up a well-respected façade, even though he has a lot of unsavory tendencies. In a literal sense, the appearances of buildings in the novel reflect the character of the building’s inhabitants. Dr. Jekyll has a comfortable and well-appointed house, but Mr. Hyde spends most of his time in the "dingy windowless structure" of the doctor’s laboratory. Other disreputable quarters of London are described as well, the stomping ground of Mr. Hyde.
Because he feels intense shame at his frowned-upon desires, Dr. Jekyll does everything he can to maintain a façade of respectability.