Many of you are studying a very specific place or historical moment. There many be a book about that place or time, however it is more likely that you find information within books about a larger topic. Check out the collections linked below to find books.
OpenLibrary Has full-text books that you can read online or check out. To check out you need to create a free account.
GoogleBooks is good for out of print books and for previewing books that you think might be useful. The most useful ways to use GoogleBooks preview is to see if you can look at the table of contents or the index and to use the search within this book function using your keywords.
SFPL has several eBook collections. They may not be research oriented, but it's worth taking a look. You will need your library card number and PIN to access.