I've heard a number of complaints about Yen Press' decision to use "Machiavelli" instead of "Villain." Personally, I don't mind it and I think it suits the context perfectly fine. Sure, it's a tad longer to say than "villain," but Shiroe's more Machiavellian than he is villainous.
Well, the LH novels are designated as being for 13 and up. Maybe my education was just weird, but I knew about the existence of Machiavelli and The Prince, and the general gist of the treatise, by the time I was that age.