Your English research assignments will require you to find peer-reviewed (sometimes referred to as "scholarly") sources.The following video from North Carolina State University Libraries explains what a peer-reviewed journal is.
Many databases and search tools have a filter to narrow your results to peer-reviewed journal articles only.
Here's an example in Gale Literature:
**Note that JSTOR and Project Muse do not have such a filter option, because all of the materials in those databases are academic.**
While you can use filters in OneSearch and in databases to limit your results to articles from peer-reviewed journals, there is no such filter for scholarly books. Some books in the library collections are what we call "popular" books, which are written for a general audience, and others are considered "scholarly" (or "academic") books. Like scholarly journal articles, scholarly books are written by experts in a particular field, and undergo a peer-review process before being published.
A quick way to identify whether a book is "scholarly" or not is to look at the publisher of the book. Scholarly books are published by university presses (for example, Oxford University Press, Indiana University Press) and by a few major private publishing companies, like Bloomsbury Academic, Palgrave-Macmillan, Routledge, Springer, and Sage. You can find a book's publisher listed on the title page of the book, and in the library record for the book in OneSearch.
You can also look up the book's author(s) or editor(s). Find their biography or CV and look for credentials like a PhD in a field related to the book's topic and/or an affiliation with a university. See if they have written or edited other books or journal articles on related topics. This will give you a sense of their expertise.
If you're unsure whether a book is an academic book or not, consult with your professor or ask a librarian.