This recent addition to Lousy Book Covers shows why a simple test would have suggested that the choice of colors might have been better...
While it might be obvious from the color version that there is not sufficient contrast between the title and the background, converting the art to gray scale emphasizes this. The original version is just barely readable...increasing the value contrast---choosing a color that is further separated from the background in gray level--would increase the readability significantly.
Looking at a histogram of that part of the cover that includes the title and the background behind it that there are no dark darks or light lights: all the grays are nearly the same.
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