See "Searching Omni" for information about searching for books, articles, videos and more. However, you can also search e-book subscription packages directly. The following collections are particularly useful for research in Politics:
Also see relevant Oxford Bibliographies e.g. International Relations. Bibliographies deliver quality references/resources with comments written (and reviewed) by experts in the field. And, yes, entries are peer reviewed. Another handbook worth checking as part of the background information gathering stage is the Routledge Handbook of Critical International Relations (2019).
Scholars Portal Books
The platform is designed to provide a single interface for accessing digital texts from multiple content providers. With a single search, you can find books from a variety of scholarly publishers.
eDuke Books Scholarly Collection
Contains books published by Duke University Press. Covers numerous subject areas including political science and political theory.
Past Masters
A collection of works, in both original language and English translation, written by seminal figures in the humanities and social sciences. Subjects covered include the history of political thought and theory, education, religious studies, economics, classics, history and philosophy of science, germanic studies and sociology.