I recently got an EDL (Enhanced Drivers License) in the US since I needed to get a new driver's license anyway. I would like to get a book for international travel eventually and I'm wondering if I have to apply like it's my first time getting one or if I can just apply for a renewal to get a book.
Assuming you are in the US (since I only know that some Canadian provinces and US states issue EDLs, and Canada does not have a passport card), you would need to apply as a first time applicant.
An EDL is not actually a passport card, even though they both Western Hemisphere Travel Initiative compliant travel documents used for land and sea travel.
Passport (book and card) is issued by the federal government, whereas EDL is issued under state authority.