Transferring from an old Clip to a new one

Ah, an addition:  are the books DRM-protected?  If so, you may need to use Windows Media Player under the Clip’s MTP mode to transfer the books and their related licenses; Audible software for Audible books; or other software that you originally used to transfer the books to your Clip.  But it should be possible to transfer the books and their related licenses (unless there is some sort of restriction associated with the files against that).