"A historian working on a particular subject is expected to show a thorough knowledge of the work of other historians in that field. They will be expected to show how their work stands in relation to these other accounts, in terms of their methodology, interpretations and use of sources."1
1. Mark Donnelly and Claire Norton, Doing History (New York : Routledge, 2011), 68.
When reading secondary sources, apply the same critical lens as you would with primary source materials.
In what context was the historian writing? Does the historian's time period have bearing on her interpretations? Does the historian's geographical location have an influence on his work? Does the historian subscribe to a particular school of thought or methodology?
What sources did the historian use or omit? Does the historian's choice of primary sources explain or limit the nature of her conclusions? Does the omission of certain primary sources affect his analysis? Is the historian responding to a previous interpretation or body of work on the subject?
An important component of any research project is a literature review, commonly known as historiography to historians. The literature review is a summary and synthesis of the existing scholarship on a given subject. Reviewing the work of other scholars--thereby identifying the major debates, questions, and possibly the gaps in the existing research--helps to place your own analysis in context. In other words, it helps answer the question, how is your research new and important?
The first step in creating a literature review is, of course, finding the literature to review. A good literature review should be as comprehensive as necessary to identify all of the major works and debates on your research subjects. Here are some tips for going beyond basic keyword searching in order to find as many sources as you can.