Choose a topic that's relevant to the publication or department. For example, if you're applying to be the editor for the financial section in a free daily in a metropolitan area (e.g. Metro New York), consider the target audience's interests and talk about a relevant topic (e.g. how to save money and spend more on the things you care about, etc.). Do choose a topic that you can realistically speak about though. It won't do you any favors if you say that you'd like to write a book on financial models if you know nothing about it.

Alternatively, you can also use this as a chance to give the interviewer a glimpse of your personal interests. A direct superior might be one person who would be interested in knowing what your interests are.

Start your response with the topic that you'd like to write a book on and, if possible, connect it with a personal experience in which you gained expertise.