Books can be used as primary or secondary sources, according to their publication date and the topic of your research.
There are three catalogs you can use to identify books on your topic:
OSCAR is the online catalog for Santa Clara University. It includes all the books, print and electronic, in our collection as well as other materials such as videos, periodicals (not ARTICLES in them!) , and government documents.
LINK+ is a catalog for approximately 70 libraries (mostly public, but there are a few academic libraries) in California. You can easily request books from LINK+ and get them in a few days.
WorldCat includes books and other materials from academic, public, special, and national libraries around the world. Materials you identify here can be requested through Interlibrary Loan. Getting books this way, though, is going to take time ... at a minimum, a week.
Online Book Collections
There are several large electronic book projects that can help you identify books and, sometimes, actually access the fulltext in electronic form (for many public domain, pre-1925, books). A few big ones are:
ACLS Humanities E-Book Project, a collection of 2,800 full-text titles offered by the ACLS in collaboration with twenty learned societies, nearly 100 contributing publishers, and librarians at the University of Michigan’s Scholarly Publishing Office.
The most difficult part of searching library databases of any kind is figuring out the language to use. Library catalogs, like OSCAR, LINK+ and WORLDCAT, are particularly difficult. You will need to spend real time figuring out the best words to use in searches and doing lots of searching!
For example, look at this description of a book in the library catalog, OSCAR: Fighting for America : Black soldiers-- the unsung heroes of World War II
That book is about African-American soldiers in World War II. If you wanted to see if we had more books about that same topic, you might be tempted to do this Simple Search:
black soldiers world war ii
Try that now and see what you get. Quite a bit, right? Notice that there are some interesting, relevant books, but, sadly, there are a whole lot more, and maybe better, books. But, to find those you will need to take a few minutes to look more closely at the OSCAR description of that first book. Consider the different words used to represent those THREE main ideas (Yes! 3!) among the Subjects listed for that one book:
For the IDEA of black you see "African American(s)".
For the IDEA of soldiers you see soldiers & also "Armed Forces".
For the IDEA of World War II you see "World War 1939-1945".
The point I am trying to make here is that you need to really look closely at the language used in whatever database you are using and be prepared to do multiple searches trying different language. Otherwise, you could easily miss out on the most important material and/or conclude there is nothing on your topic!