[CharlesW]

> What are the differences between the two from an author's financial perspective?

The short answer is that libraries buy books, pirates don't.

In regards to physical books, a good place to start is understanding "first sale doctrine"[1], which allows both libraries and you to do what you want with a book once you're purchased it.

First sale doctrine does not apply to DRM-encumbered ebooks, so libraries must buy as many licenses as they wish to loan, paying three-to-five times the retail price for each limited-time license, and re-purchasing those licenses when they expire (typically after two years).

[1] https://www.nolo.com/legal-encyclopedia/the-first-sale-doctr...