Well, this is rather lovely! The Paravel gang have made an atmospheric web book out of a Sherlock Holmes story (yay for the public domain!).
Can an opinionated flat design still have depth and truly be free of drop shadows?
Scott proposes a technique that mimics atmospheric perspective—y’know, when things in the distance look hazier than things in the foreground.
The fact is, we are surrounded by a world that is full of depth, and very little of it is defined by shadow. If we are going to replace drop shadows in our visual UI metaphors, we should look at other options that create depth in the world around us.
All those ambent background movie clips and adverts in Children of Men. There's a lot of attention to detail here.