A critical theme in modern digital publishing is the distinction between purchasing a physical copy and licensing a digital one.

: Publishers use DRM to restrict sharing, reselling, or backing up books to non-approved devices.

: Most online book platforms, such as Amazon Kindle Store and Apple Books , sell access licenses under specific terms of service rather than true ownership.

: Digital libraries are subject to platform control; accounts can be closed or licenses revoked if a service shuts down, leading to what some researchers call the "erosion of ownership". 2. Trends in Online Book Purchasing