To find books and government documents in USA Libraries' collections, use SOUTHcat: USA Libraries' Catalog.
The USA Libraries subscribe to several subscription e-book collections. These collections tend to focus on a specific discipline or field of study in their coverage.
To find items on your topic that are not within the USA Libraries' collection, try Worldcat and Google Books. If you find something useful, we may be able to get it for you from another library via interlibrary loan.