It’s entirely possible I spend too much time with my head buried under a rock, but I just recently became aware of the Library of Congress Mandatory Deposit for all print materials.
If you are planning to self-publish, I strongly recommend heading over to the Copyright website and familiarizing yourself with copyright laws.
In addition to the copyright information, pay attention to the document called Mandatory Deposit.
Yes, there is a “poor man’s” copyright, but make sure you educate yourself on all the basic details of copyright laws.
You can register your work online and it is a fairly simple process.
Don’t wait until you think you have time to read through the info. Do it sooner rather than later and make yourself aware of the requirements and laws.