The Library of Congress is owed two copies of your book.
"U.S. copyright law (17 U.S.C. § 407) requires every published book to deposit two physical copies of the best edition at the Library of Congress within three months of publication. Most indie authors do not realize the obligation exists."
How to comply: send two copies of the best edition (hardcover if available) to the U.S. Copyright Office for the Library of Congress, Washington DC.

