Each illustration is accompanied by the usual little notice telling you something about it, and in the case of the classics they often include quotes from the books. In the case of Jekyll, one is particularly interesting. Peake - after some preliminary attempts - decided not to show Hyde's face, because it's described as pure evil (always tricky to draw, I'd guess) and also because nobody who sees it can remember much else about it. So in the drawings actually used for the book we never see Hyde's face, only his back or his hands. The passage that struck me as familiar is a description of Hyde's hand on the bedclothes, and is taken from Chapter 10. The hand is described as:
...corded, knuckly, of a dusky pallor and thickly shaded with a swart growth...This struck me as familiar. I have of course read Stevenson's story, but it bears a strong resemblance to an even more familiar tale:
Pale, dusky skin, covering nothing but bones and tendons of appalling strength; coarse black hairs, longer than ever grew on a human hand; nails rising from the ends of the fingers and curving sharply down and forward, grey, horny and wrinkled.From 'Canon Alberic's Scrap-Book', by M.R. James. This has probably been pointed out before. But I'm sure the young Monty James read his fare share of Stevenson, and it would be surprising if some images - especially the scary ones - hadn't taken root.
Here's the famous McBryde illustration for the story.