There are a lot little intricacies about copyright law pertaining to illustration that are commonly misunderstood – mainly that the producer of the book needs to buy all rights to the art in order for it to be included in a book. I talk more about that in my post titled "Authors Who Plan to Self Publish – You Don't Need All Illustration Rights!"
I've found a great resource that I think anyone who works in the publishing business should read. If you are an illustrator, please read this, too. The more knowledgeable all of us are, the easier it will be to maybe get what our work is worth! It's a booklet written by illustrator Randy Gallegos and can be downloaded for free on Randy's blog.
Thanks Randy for this great resource!