When I study this cover, first-and-foremost I see an expression of rage - which isn't usual for Superman. His fists are coiled, balled up in anger. Notice too how the dialogue balloon on the right side of the cover is jagged and sharp, emphasizing the rage inherent in the Man of Steel's words ("I'M TAKING YOU WITH ME - all caps!). Also, as the cover is laid out, there seems to be a source of light (like a sun or something...) behind Superman, I'd guess at shoulder level. An intense light...gradually getting less intense as it moves away from him. By featuring it behind him, and in that position, it makes Superman the fulcrum of intensity in the composition. As though his anger is creating light - energy - itself. I think the feeling Howard describes - shock - is exactly what the cover intends to convey; the notion that Superman is mad as hell and about to kill someone. Everything in this cover, the jagged balloon, the intense light behind him, the all-caps, the balled fists, convey this notion. Also, the reflection of green on Superman's face tends to make him look even more murderous and abnormal, which is important to the idea that the universe portrayed here is disordered, wrong (hence, shocking or surprising). On a very basic level, this is also a look at idealized masculinity turned inexplicably angry and violent.
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