My work actually came under copyright protection from the moment I had created a manuscript. Copyright registration is highly recommended, because it means a given work is in the public record, and in addition all registered works may be eligible for statutory damages and attorney’s fees in successful litigation, and more importantly, the United States has bilateral and multi-lateral copyright agreements with most countries throughout the world.
In anticipating the fact that you will have many questions about copyright registration, follow this link to review a long list of pertinent frequently asked questions: http://www.copyright.gov/help/faq/
To register my work, I logged onto www.copyright.gov and created an account. Because I had already entered into a contract, a work for hire agreement with an illustrator, I actually own the rights to all of the illustrations, so in my case I had to apply twice to register my work: first for the text, and the second time for the artwork. After completing the application process and uploading the files, the certifications were sent by snail mail to the address I provided. It usually takes up to 6 months to receive the certifications. If you wish to get your certification earlier, it is possible do so within a 10-day timeframe, for a fee of just over $700. On the second published book, I have only mailed myself a copy of the manuscript as a reference in case future matter appears.