1. When first searching use a broad KEYWORD. Make sure to use the most recent scholarship by sorting the results by date.
2. Once you've found an item that looks promising, take a look at the subject headings assigned to it (they are blue and underlined). When you click on the link, it will take you to a list of every book in the Library with that same subject heading. This is a good way to narrow your search results.
An Overview is a book which addresses a time period such as Early Modern Europe: An Oxford History. Use the index to find your topic; it may be a chapter or just a few pages. An overview is meant to place your topic within the context of the time and larger world.
A Monograph is a book which addresses your specific topic. If you are researching a person, a monograph could be a biography of the person. If you are researching an event, a monograph might be The Thirty Years War: Europe's Tragedy.