Another of the all time classics, thanks to a great premise. And again hard to say anything new about something that's been so often analyzed. 
 So just a few thoughts--pretty much every adaptation of this story in other media reverses the structure, foregrounding Jekyll's transformation rather than Utterson's investigation into the mysterious connection between his good friend and the horrid Mr. Hyde. And for visual coding, Hyde is almost always depicted as monstrous in appearance rather than subtly wrong. Thus reading the book is an entirely different experience. 
 Stevenson is also frustratingly vague about just what Hyde does outside of shove over a little girl (not even on purpose, it seems) and murder a man in a fit of rage. "A certain gaiety of disposition"> What does that even mean? It's telling, though, that Jekyll doesn't try turning himself into a being of pure good.