A literature review is a document summarising and critiquing the academic literature on a given topic in a given field. For instance, I am currently writing a literature review on how different linguists have approached the emergent property problem in accounts of metaphor, as preparation for writing my dissertation. The goal with a literature review is to demonstrate familiarity and understanding of a topic's academic landscape, and find problems or gaps in the current research. This article is written to show you how to do so effectively.
The (hopefully) obvious first step is to assemble the literature: the sources you will be summarising and critiquing in the review. Your tutor may have provided you with a list; if not, then you are tasked with finding sources which pertain most directly to your subject area. See our article on How to research better for advice on this. It is important that you collate a balanced set of references, as one of the aims of a literature review is to establish a broad overview of a topic's academic consensus (or lack of).
It is best to start by reading and summarising the core content and argument of each source. This will help you to make sense of the academic narrative. Then, you should read your sources again, but this time with a critical eye, asking questions of the material by picking apart things like methodologies, assumptions, hypotheses, and so on. By doing this, you will gradually construct your own line of argument in light of the topic's contemporary landscape. Read up on Stanford's three-pass method for a methodical approach to reading academic papers.
Finding the gap
Often, the end goal with a literature review is to use it as a springboard for one's own research, hence the important of finding a gap in what already exists. Even if this is not the case, finding a research gap demonstrates strong critical analysis skills anyway, so should be considered essential to a literature review in most cases. But what exactly is a research gap?
The answer is that it can take a number of forms, but generally appears as an unexplored/unanswered perspective, problem, or question in the current literature. A research gap is critical for establishing a research question, but finding one is often the most challenging component of a literature review. While there is no universal method for identifying a research gap, what is always required is a comprehensive review of the most up-to-date research, and perhaps some quiet reflection and creative meditation on what might be missing.
Before you begin the write-up, make sure you have a clear focus. Your goal is not to consider every single argument and perspective, only those that pertain to the topic. The topic should be narrow enough for you to write insightful but concise summaries of the most current literature without waffling.
It is important you structure the write-up in the right way. Yes, this means an introduction, main body, and conclusion. Your introduction should introduce the topic and the core arguments, providing a roadmap for the review.
The main body is a little different; there are numerous ways of structuring this content. You might do this chronologically, thematically, or even methodologically, depending on the subject area and nature of the literature. What matters most is that you present a clear, coherent narrative on what has been found thus far, in a good amount of detail. Having summarised the core arguments and perspectives, you need to show a critical evaluation of those ideas; this is what a literature review is really all about. You must be sure to link your evaluation back to your topic/research focus, highlighting why a particular theory, argument or method fails to contribute real value to the issue in question. In a sense, this is like providing evidence for why your own proposed research is not only promising but necessary.
The conclusion should firstly restate your critical analyses of the literature, highlight why these expose a gap in the research, and how your future work (or, if a standalone literature review, the future work of others) needs to fill this gap.
This is essentially what it takes to produce a strong literature review. If you are still a bit stuck, you can find a good sample literature review here.