The right answers are "What type of text is this? ", "What is the central idea? " and "How does this text make one feel?".
These questions would be best suited for the reader to identify the author's purpose in writing because they are in the "soul" of the written work. Questions like "What type of reviews did the book receive?" and "How many copies of the book have been sold?" serve only to know about the audience that that work was having and not about its purpose.