The first place to check for books on your topic is the Catalog.  Here are some quick tips for effective catalog searches:

If you are looking for books by a writer, use the Author search (last name first).

If you want books about an author, use the Subject Heading search (last name first).

Here are some subject headings you may find useful:

• Spain - Civilization- 1516-1700
  
• Spain - History - 18th Century
• Spain - Politics and Government
• Spain - Social Life and Customs-
  
• Spain--History--House of Austria, 1516-1700
• Spain--History--Ferdinand and Isabella, 1479-1516.
• Spanish literature--18th century--History and Criticism
  
• Spanish literature--Classical period, 1500-1700--History and criticism.

Of course, you can also use keyword searches.