This article is from the Children's Books FAQ, by Hilary Morrison, email@example.com with numerous contributions by others.
The simplest way is care of the publishing house. Most books contain the
address of the publishing house on the cover page. If a particular one does
not, you can look it up in a directory of publishers at your local library.
Ask the reference librarian for assistance if you need help finding
something. An increasingly common theme is for authors to have their own
official web pages, usually with a way to contac them. The HotBot search
engine (http://www.hotbot.com) allows you to search specifically for a