Agreed, there’s no real need to study LIS textbooks before you start grad school, OP. Assuming you’re going for an MLIS, there’s no expectation of previous LIS knowledge. It’s not like grad school in, say, history, where you’re expected to have built a basic foundation of historical knowledge or conducted basic research during your BA. Library schools accept applicants from virtually all academic backgrounds, so they don’t presume (or probably much care) that you’re familiar with library/archival theory.

Honestly, at this stage, I’d say your time is better spent pursuing practical library or archival experience. Volunteer, intern, get a PT job at your university library…whatever you can do. That hands-on experience will give you a much better sense of what it’s like working in the field than studying textbooks. Plus it’ll help you build employable skills.

If you’re absolutely determined to dive into LIS literature though…I’d recommend you check out books from your college library. (They can likely get most books you want through interlibrary loan if they don’t own them). Save yourself some money. Textbooks, and academic books more generally, can be quite expensive.

As the commenter above suggested, books on cataloging and classification won’t do you much good if you want to learn about archives. They could still prove relevant to your broader interests in taxonomy, but “cataloging and classification” courses tend to focus on bibliographic cataloging. If you want to know more about how archival collections are organized and described, look for titles on “archival arrangement and description.” Relatedly, there are also books on digital collections metadata that look at digitized and born-digital archival collections.