Writers spend a lot of time wondering about other writers. They study them, emulate them, envy them, and, when one or two emerge as very successful, they bad-mouth them. Always there are questions that writers would like their colleagues to answer about their work, their lives, their miserable success. So, in that spirit, we posed this to writers participating in this year’s National Book Festival: If you could ask one question of one writer, what would it be? Here are their answers — or rather, their questions.