Coelho states: "i am not a self- writer; i am a self-problem writer". what does this mean and how could this impact the writing style of the novel?

It means he does not write to solve problems, he writes about the problem itself. 

The full quote is I am not a self-help writer. I am a self-problem writer. When people read my books, I provoke some things. I cannot justify my work. I do my work; it is up to them to classify it, to judge.

So he is writing about his own problems and how he resolves them; rather than telling others how to resolve their problems. It allows Coelho to easily reach his readers.