I love this list of the “20 irrefutable theories of book cover design” from the Guardian:
11. Unheimlich theory
This theory takes a familiar image or symbol and makes it strange or unsettling. One cover of Lolita uses the image of a girl’s bedroom wall to represent a girl’s legs and underwear.12. Absent presence theory
A gap is left on the cover, a missing image or text, that implies something. By having this space, the reader is forced to fill the gap with their imagination in order to understand the meaning.13. Ju Jitsu theory
The opponent, the cover, forces a view or conception upon the defender, the reader, such as the bloody, violent implications on the cover of Anthony McGowan’s love story Stag Hunt.
It speaks to the former graphic designer in me, as well as the lover of seeing trends and movements that may not really be there yet, drawing on threads to bring them together. Plus, you know, “Unheimlich theory” is just a great name for anything.