Tagline / hook — one or two lines, top of cover, large type
Back cover copy — the main sales text, typically 150–200 words
Endorsements / blurbs — quotes from credible names, with attribution
Author bio — short, 50–75 words, usually with a small author photo
Series information — "Also by..." or series branding if applicable
Category / genre line — e.g., "Self-Help / Anxiety" — tells booksellers where to shelve it
ISBN barcode — bottom right, always
ISBN number in text — printed above or near the barcode
Price — printed on the barcode block or separately; sometimes omitted on hardcovers
Publisher logo — bottom left typically, or bottom center
Publisher website — small type, often near the logo
"Printed in [country]" — sometimes included, sometimes on the copyright page only

Primary — Recommended

Tagline / hook
Back cover copy
Author bio
Category / genre line
ISBN barcode
ISBN number in text
Publisher logo

Secondary — Optional

Endorsements / blurbs
Price
Author photo
Series information
Publisher website
"Printed in [country]"


Bowker (myidentifiers.com) is the only official US ISBN agency. Single ISBN costs $125. 10-pack is $295.
ISBN.org barcode generator — free, official

Free: Amazon
https://www.myidentifiers.com/identify-protect-your-book/isbn/buy-isbn  -- ** for multi-platform publishing

This changes your math on Bowker packages significantly. If you're planning translations, the 10-pack at $295 becomes the obvious move.

Formating EPUB (for all platforms)
https://www.isbnservices.com/product/ebook-conversion/
FREE:
https://draft2digital.com/
https://draft2digital.com/register/

Official US Copyright registration:

Copyright:
Done through copyright.gov
$45-65 for a single online registration (basic claim)
Takes several months to process, but registration date is the filing date
Gives you full legal teeth if someone copies your book