Write for yourself: you're the only audience you need

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"I love reading your tweets and blog posts, they aid my indie publishing journey! I want to write a compelling, hip sci-fi thriller in a futuristic European Union, which I know very well (I'm from Germany), but I don't know if Americans, my main target audience, would even read about that 'exotic' place, since most English works play in the US. Old gossip says Americans generally don't read about stories in other places than their home. I'm curious, since you're originally from...