A literature review is both a process and a product. This guide focuses on the process of doing a literature review. As a process, it involves searching for information related to your topic, to familarize yourself with the relevant research and to identify issues and gaps in the research. In most cases you're seeking to identify the key authors and key arguments that are relevant to your topic, not to exhaustively read everything written on the subject.
Whatis a literature review?
"Literature reviews are systematic syntheses of previous work around a particular topic" -- Card, Noel A. "Literature Review." In Encyclopedia of Research Design, edited by Neil J. Salkind, 726-29. Thousand Oaks, CA: SAGE Publications, Inc., 2010.
Note the term "syntheses" - most literature reviews go beyond mere summarization and involve a certain level of analysis
To broaden your own knowledge of the research area
To clarify and focus your research question
To situate your research in the context of related research, and identify gaps in the literature that your research may address
To improve your methodology by learning what tools and approaches other researchers have used
Source: Barron, Lee. "LITERATURE REVIEW." In The SAGE Dictionary of Social Research Methods, edited by Victor Jupp, 163-64. London, England: SAGE Publications, Ltd., 2006.
Whenshould the review be conducted?
BEFORE you start your project. Remember, it’s meant to inform the rest of the project – don’t bake the cake, then try to concoct the recipe!
Howcomprehensive/systematic should it be?
That depends – there are different types of literature reviews, some of which aim to identify every published study on the topic. The literature you review should be a representative but not necessarily exhaustive synthesis of the literature surrounding your topic or question.