An Overview is a book which addresses a time period such as The Cambridge History of China. 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 Opium War, 1840-1842.
1. Try a KEYWORD search for "Opium War" or Qing dynasty
2. When you find a book in your search results that looks relevant, use the subject links for that book to lead you to more sources.
Example: China -- History -- Opium War, 1840-1842.
Example subjects covering topics related to the Qing Dynasty and the Opium War: