^I think costume is a part of fashion and if it isn't, it certainly is influenced by fashion.
The costume designer is someone who studied fashion, if it's a period movie, the designer had to study the fashion of that time. A book that describes a beautiful dress could be inspired by some dress the writer saw in a store, and that would qualify as fashion. So even if the clothes described in the books aren't fashion, they are influenced by it. Which means that indirectly you were influenced by fashion.
And now about the person dressing sharply, where is this person gonna buy clothes? A fashion store, and if you want good clothes, well-made, good material, the guys who did it would have some knowledge on it.
For you to not be influenced by it and dress well then you would have to be Tarzan, completely away of society and with lots of creativity. So I think that in our society of today that's pretty impossible. Maybe an indian or something.
