TRAPS: Believe it or not, this is a killer question because so many candidates are unprepared for it. If you stammer or ad lib, you've blown it.

In formulating your answer, be sure to address these areas:

1. Determine their goals for the position. This should come up during your research into the company and into the position. If possible, talk to others who work for the company. If you are unclear on this point, include it in the questions you ask at the interview itself and be prepared to incorporate it into your answer. 
2. Show you have the skills needed for the job. Based on the goals you have identified in step one, determine how your skills and experience support those goals.
3. Articulate shared values. Again, this should come up in your research. Look at the company’s mission statement and regular business practices. Explain why these are in line with your own values and goals. 
4. State your interest in the position. Be enthusiastic about the opportunity to work for this company and/or within a certain team. Be sure that the interviewer is clear about the fact that you want this job. 
BEST ANSWER: If you know the employer's greatest needs and desires, this question will give you a big leg up over other candidates because you will give better reasons for hiring you than anyone else is likely to, reasons tied directly to their own needs.
Whether your interviewer asks you this question explicitly or not, this is the most important question of your interview because they must answer this question favorably in their own mind before you will be hired. So help them out!  Walk through each of the position's requirements as you understand them, and follow each with a reason why you meet that requirement so well.
Example: As I understand your needs, you are first and foremost looking for someone who can manage the marketing of your software products. As you've said, you need someone with a strong background in trade book marketing. This is where I've spent almost all of my career, so I've chalked up 18 years experience exactly in this area. I believe that I know the right contacts, methods, principles, and successful management techniques as well as any person can in our industry.
You also need someone who can expand your book distribution channels. In my prior post, my innovative promotional ideas doubled, and then tripled, the number of outlets selling our books. I'm confident I can do the same for you.