I could see this is if the title was "for morons" (or something like it), something implying a class division. But 100% of humans are mortal. Everyone is mortal, including the author. So there's no real division here, no two tiered system: we are all on the mortal tier.
For that matter, the For Dummies books have subtitles that refer to "the rest of us". So the actual reader as well as the author are not necessarily one of the dummies.