I wrote a paper that I registered for copyright a few years ago.  It was not published.  I am now completing a book length work that incorporates the unpublished paper.  Can I register the new work separately?

Section 408(e) of the Copyright Law states that “Registration for the first published edition of a work previously registered in unpublished form may be made even though the work as published is substantially the same as the unpublished version.”  

On this authority, if an author may register for copyright the same material again, even more so can she register a new work that incorporates the prior unpublished paper.  Added material in later editions of a work may also be registered.  The copyright form provides boxes for checking off previously registered material. It also provides for exclusion of the earlier (already registered) material from the new copyright claim.