If you plan to sell your book to libraries, you’ll need a Library of Congress Catalog Number, aka an LCCN.

You can order your own through the website of the Cataloging in Publication Division of the Library of Congress. The best news is that applying for an LCCN is free, so it makes sense to simply add an LCCN when you self-publish a book.

A book must be longer than 50 pages to qualify for an advance purchase of LCCN. Because of this, many children’s books typically don’t qualify.