I have mixed feelings about "dummies" titles... nothing against the series, just the use of "dummies" in the title. While the word can make some flinch, there is also a bit of humor involved in quickly communicating that no background knowledge base is needed...
The titles are meant to put potential buyers at ease, as in,
a dummy can learn this. Don't panic. We explain stuff coherently and in detail. Anyone who's familiar with the series knows that a lot of those books aren't for actual dummies (e.g., Differential Equations for Dummies, Quantum Physics for Dummmies).