If the plan is to sell books to libraries, a LCCN (Library of Congress Catalog Number) is needed. The LCCN assigns a library cataloguing number to books. A LCCN number can be attained at: www.pcn.loc.gov . CIP (Cataloging in Publication) number is often used for library cataloguing, and excludes self-publishers and publishers with fewer than three (self-authored) books.
The LCCN appears on the copyright page of a book. Consult the copyright page of books published by major publishers for correct placement. When typesetting the book, order the LCCN number. Send two copies of the printed book to the Library of Congress. (Address provided below.)
Library of Congress
Cataloguing in Publication Division
Washington, DC 20540