Daniel replies:

If your friend's publisher should send me review copies of your friend's books they will stand the same chance (one in several hundred) of being picked for presentation on the air. If you and your friend, and perhaps 500 other people should write to NPR suggesting they have us talk about a children's book every week, instead of every month, NPR will ignore the letters and leave things just as they are--but if they didn't the odds would improve.