We have discussed Gabriel's requirements for book covers before, I'm sure - almost certainly in a podcast - but when he was telling me about a new Alastair Reynolds book, I did a quick search for the man and saw this:
And I'm sure that this level of utter synchronicity is probably the result of a branding refresh or something, judging from the dates. That said, I also think the audience for hard sci-fi operates as a kind of wind tunnel that optimizes this shape. It's a survival adaptation, essentially; carcinization, but for covers. I suspect that the retail book shelf is a caustic, deadly environment, comparable to the Battle Bots arena, where a similar scenario is eternally retold. There were all kinds of crazy-ass morphologies at the start and now it's sort of understood that if you aren't making a wedge of some kind you might as well take your stupid robot out into the backyard and destroy it yourself.
I could read one of these books at any time; it would be a trivial matter. I know where such books might be secured. But I don't think I would enjoy it anywhere near as much as I do his meticulous recitations of these plots, arrayed as they are upon a substrate of nearly absolute joy.