In a Zettelkasten system, literature notes are notes about a specific piece of literature (book, paper, etc). They are mostly brief notes that are meant to be turned into permanent notes then archived. These notes stay with the reference page to the book/article and contain citation keys (e.g. from Zotero, so annotate within Zotero and export later). The benefit of having a literature note is that other permanent notes can cite it as the source, and if the book turned out to be wrong, we can trace what notes the literature note affects and fix the mistakes.
Avoid writing permanent note as you read
Try to avoid writing permanent notes especially while reading humanities-related materials, because the information you gain may not necessarily be correct, agreeable, or coherent with existing notes. A better approach would be to take fleeting notes in the literature note first and process them into permanent notes that are correct and consistent with existing slip-box notes (or modify existing slip-box as fit) later.