Reference works are an excellent first stop in your research and are incredibly useful for the following:
Reference works are a good starting off point, but should not be cited in your research as they are not considered primary or secondary sources. The only exception is when reference works contain primary and secondary sources (like collections of documents and essays).
Handbooks are general information sources which provides quick reference for a given subject area. Handbooks are generally subject-specific.
Encyclopedias and dictionaries provide excellent background/overview information, providing an excellent way to begin research. Many provide bibliographies for further reading. Mostly located in the second-floor reference collection from approximately HA-HJs, here's a sampling of resources available: