

I’m honestly surprised that isn’t already the case. The first year of college 101 courses in America are often just rehashes of high school. Because the American high schools are so inconsistent, that the university wants all of their incoming students to at least have the same baseline. I went to a decent high school so it was 100% repeated content for me. If given the option, I could have skipped the entire first year of classes. But I had a shocking number of classmates who apparently had never seen anything past basic quadratic equations before.
Calibre doesn’t natively support reading DRMed files, but there are anti-DRM plugins which are trivial to install. You need to provide a legitimate Kindle serial number for Amazon DRM, as it uses that to de-encrypt the files. When you add the file(s) to your library, the plugin automatically runs as a file conversion. It basically converts it from a DRM-locked .epub/.azw3 to a DRM-free .epub/.azw3 instead. Since Calibre already has file conversions built in, the plugin simply uses that existing system to spit out a DRM-free version of the same file, then it adds that to your library instead.