The European Union is the result of an economic and political partnership between European countries. Originally devised at the end of World War II, the EU consists of a number of different institutions that negotiate intergovernmental decisions in various areas, including business, law and economics. It has a parliament elected from member countries.
A good staring point for your research is the EU itself, which has resources on its webpages regarding EU history, institutions and documents. In addition, you can use the library's search tool OneSearch to find recent books, academic, and news articles on the EU and Brexit. The library's political, economic and business databases are also good sources of information