Try your local library first for books and magazines. If the public library does not have the kinds of books you need, a nearby school or college may. You can go there and take notes.
Some libraries have collections of government documents.
Books or manuals available at your present job may be useful as well. If you have Internet access, you may want to search the web for information on a particular topic. Many libraries have Internet access and can help you with your search. There are some private companies that publish examination study guides on particular jobs. These are available in libraries or bookstores and have titles like Civil Service Examination for Accountant .