The covers.
The Harry Potter depicted in this cover seems strikingly different from the Harry we have known and loved for the better part of the past decade. Considering the impossibility of "the task" and the inexorability of "the path", the bruised faces of the trio, the look of shock (or is it of fear and revulsion?) on Hermione and Ron's faces and Harry's determined and brave expression are perhaps understandable. If you look hard, you would be able to spot the grayish-blue ear, forehead and hands of Dobby, who seems to be holding Godric Gryffindor's ruby-encrusted sword and literally and figuratively standing behind Harry 100%. As for the artwork on the extreme left corner, I've a sneaking feeling that that snake is Nagini and that she is being viewed in one of Prof Trelawney's crystal balls -- serving as a sign of how Trelawney's divination would be of some practical use at last. The leaf-less tree outside the Hogwarts castle seems like the Whomping Willow and the white deer on the right obviously represents Harry's patronus, something which would play a prominent role now that the dementors would be floating around freely, what with Voldemort in-charge of who infests the alleys and tortures the innocent.
The UK Adult version on the other hand, doesn't seem to give away as much detail as the children's one. The locket obviously depicts the Slytherin family's heirloom, the one that Merope Gaunt (Voldemort's mother) sold to Mr. Borgin for a mere 10 gallons (that's a wizarding currency, ye ignorant fool). From what I can extract from my memory, this locket served as one of Voldemort's 7 Horcruxes and that it was the last Horcrux that Dumbledore found, only that it had already been destroyed by someone by the initials R.A.B. Although I cannot see how it serves any role prominent enough to land it on the cover, I feel it looks radically aesthetic than what I might have expected it to be, after many centuries of being handed down from one generation to another and a couple more centuries of it being screwed about by the Gaunts.
-| AG.
-| AG.