Subject encyclopedias can provide a good starting place to familiarize yourself with a topic. They also provide bibliographies for further reading that show you some possible next steps for your research.
If you have a good book or article, other scholars probably have noticed too! See which other scholars have referred to the book or article you have in hand and extend your research. Looking up a title in Google Scholar (link to the left) and paying attention to the "Cited by" link can be a very helpful search strategy.