Richard J. Light & David B. Pillemer 
Summing Up [PDF ebook] 
The Science of Reviewing Research

How can a scientist or policy analyst summarize and evaluate what is already known about a particular topic? This book offers practical guidance.
The amount and diversity of information generated by academic and policy researchers in the contemporary world is staggering. How is an investigator to cope with the tens or even hundreds of studies on a particular problem? How can conflicting findings be reconciled? Richard Light and David Pillemer have developed both general guidelines and step-by-step procedures that can be used to synthesize existing data. They show how to apply quantitative methods, including the newest statistical procedures and simple graphical displays, to evaluate a mass of studies and combine separate data sets. At the same time, they insist on the value of qualitative information, of asking the right questions, and of considering the context in which research is conducted. The authors use exemplary reviews in education, psychology, health, and the policy sciences to illustrate their suggestions.
Written in nontechnical language and addressed to the beginning researcher as well as to the practicing professional, Summing Up will set a new standard for valid research reviews and is likely to become a methodological classic.