Children's books are a staple of small booksellers

The Right Mix: Kids and Adults

This article refers mostly to new books, and is therefore out of my jurisdiction, but I can still see why juvenile literature remains such a big seller. Younger readers are constantly developing, both in reading ability and in subject interest. As they acquire a larger vocabulary and better reading comprehension, a six year old may like Clifford one week, and Harry Potter the next. (and Gore Vidal the next?) Children's books are usually paperbound and short on content, 10-30 pages. It is easy for a publisher to churn out hundreds of these titles, and in a fashion that lends more towards reading inhalation than book collecting.
We sell a fair amount of children's books, mostly around Christmas time. The difference is that our customers are usually looking for books they read as a child, either for collecting or to pass the title down to younger generations. They are looking for specific titles, editions, and conditions. Our current stock stands at about 15% juvenile, if you count our children's history, reference, and religion sections, as well as our series books like Nancy Drew, etc. In any given month, I would say that maybe 5% of the books sold are children's books, so maybe we should clear that section out or have a sale!