Richard A. Posner, .. Harvard Univ., $35 (464pp) ISBN 978-0-674-00485-6

Posner, a federal appellate judge (he was chosen to mediate the recent Microsoft antitrust case) and legal scholar (at the University of Chicago), examines the points of connection between law and a series of related fields, including economics, psychology, history and statistics. The purpose of the study is to determine whether these other disciplines can inform and improve the American legal system. Posner's central interest remains the intersection of law and economics, an approach featuring cost-benefit analysis as a tool for making policy choices and for steering judges toward efficient decisions. Some of the discussion is technical (e.g., regression analysis) and will be accessible only to specialists. Other chapters contain Posner's responses to recent articles by other leading adherents of the law and economics theory, and so will appeal to an academic readership. There are, however, other sections of the book that seem to reflect the author's experience in the courtroom rather than in the seminar room, and these passages are fully accessible to the general reader. For example, Posner offers insights into such controversial issues as hate-crime legislation, controls over speech on the Internet, the costs and benefits of the jury system, and the standards for excluding categories of evidence from trial. Posner's take on these issues is unfailingly original, crisply expressed and appropriately qualified by recognition of the limitations as well as the strengths of theory applied to real-world problems. Whether you agree with his conclusions or not, Posner demonstrates how to think hard and systematically about law. (June)