The library IS a good starting point. Repeat after me: library.princeton.edu, library.princeton.edu, library.princeton.edu
No need to Google it.
catalog.princeton.edu is a good starting point for books
Let's practice converting a "keyword search "into a search using "controlled vocabulary" --the Library of Congress Subject Headings. For example, Obamacare, or Covid-19, or anything you'd like to try.
Alternatively, you can explore possible Library of Congress Subject Headings suggested by the Health Policy Librarian, Joann Donatiello.
In addition, for US information you can use CMS Centers for Medicare & Medicaid as an author.
Google Scholar on your text “Health disparities in the United States : social class, race, ethnicity, and the social determinants of health / Donald A. Barr.”
Limit by recent and/or covid