Background information is useful to any research project. It helps you and your reader understand how your topic fits into the context of the larger issue at hand and why it is important.
Using Handbooks and Encyclopedias is a great way to understand the nature of an issue before you begin looking for research on the topic. It is easy to approach a topic with our own personal biases and therefore reject good sources that "don't say what we want them to." That is not a good scholarship practice.
These select sources with help give you background information on the issue/ topic as a whole and understand how topics fit together.
