Legal Question in Intellectual Property in Illinois

I assume you have written letters demanding an accounting and payment of the royalties. If not, that should be your next step. If the publisher ignores you, your only real mechanism to collect your royalties is to sue. Assuming Illinois courts have jurisdiction over the publisher, and the amount you seek is under $10,000, you may file an action in small claims court. Of course, getting a judgment still doesn't guarantee that the publisher will promptly pay you. You may then need to take steps to enforce the judgment.