I love the covers for Superposition and Supersymmetry.  They don’t exactly depict any character or situation from the books, but they capture the books thematically, and they’re certainly eye-catching.  But I’m afraid that casual bookstore browsers won’t notice that these are, in fact, two different books!  So here’s a shout-out to all readers of Superposition wandering through bookstores in September: You didn’t already read this one!