Today’s software tools have weird names. We call a “library” some collection of functions that you can use in your program.
I think that software repositories (where apt downloads your programs from) should be the actual libraries, since that’s where you go to get your information; Meanwhile individual packages of information should be called books because they are one solid object containing a bundle of information.
books is a specific type. library is just a different word for collection. So calling them books would be wrong. Because library does not imply a book. In example you can have a library of videos or a library of images.
You are right, but I do want to point at that “library” is based on the Latin word librarium which literally translates to “a place for books”.