I don’t mean to distribute, but to scan for myself to read digitally, am I allowed to do that legally and ethically when I buy a physical book or would that be totally unethical and illegal?
You are legally permitted to do so, but not entitled.
What’s the difference? DRM.
If you license a digital work, you are allowed to make copies for personal use. However, if the publisher includes features to prevent replication, you are not entitled to make a copy; in other words, publishers including DRM to prevent replication of their works is not illegal because you do not have a right to copy digital works you license, but you are allowed to do so.
I believe the distinction is you have a right to copy for own use/backup but you don’t have the right to break the DRM preventing you from doing so.
For example, you have a right to make a copy of a video game (by installing it to hard drive) but DRM willl prevent you from running it unless you have the original disk in the drive.
