She wrote "Coming out of the Dark" after her tour bus accident, which left her with a iron rod in her back. She wrote it as a "thank you" to her fans for all of the support that she had during her...
It actually depends. You would use which if you were asking what book they wrote among a certain selection of books. You would use what if you were just asking in general.
You learn how to write a book. Here are some links to get you started -- then you go get some How-To-Books or take some classes! It's either that or get ready to hire someone to write the book --...