This sounds like the writer is trying to be clever and he's losing his audience in the process. I don't really get what he's trying to say. You can say published writer or published author.
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NewguestHe follows that in his life he suffered kicks (I understand he was having a hard time), so in the process he became callous (hard back).That's how I interpreted it too, but for me the wordplay falls flat because I have never heard this expression "hard back".
AnonymousIf you don't get a simple wordplay you shouldn't be a translator in the first place. Are you planning to ask about every single phrase from the book while translating it?The problem with your post, Anon, is that two native speakers didn't "get it" either, since the word play doesn't play on a standard idiom or a know expression.