Jurists around the world know that the value of the law lies not only in its content, but also in its form.And no aspect of legal formalism has interested comparatists as much as the extent of legislative codification or non-codification across legal systems. It is well known that civil law systems have a tendency to favor the codification of law—or at least the codification of certain bodies of law—whereas codification, as it is typically understood, has not found special favor in the common law. But the questions surrounding codification are far more complex than any simple dichotomy between civil law and common law systems can possibly capture. This is due in part to the complexity of codification itself. Thus, codification can itself take different forms and is, in any event, a matter of degree, since in no system is the law fully codified. Conversely, no modern system—no matter how unreceptive it may be to codification as a legislative method—is without codification altogether. Even in a legal system that has long enjoyed codification, codification reform occurs, and not only because the content of the law has evolved. Codification cannot be, or should not be, static, so that even largely codified systems need to address the challenge of maintaining over time the coherence and systematization that codification promises, even as the law itself evolves. Thus any study of codification also entails processes of de-codification and recodification as well. We also know that, even limiting ourselves to largely codified systems, codification differs importantly in methods and results from country to country. Not least, different fields of law lend themselves differently to codification. This last observation caused the architects of this publication to build it very largely around fields of law, so that the distinctive experiences in codification across fields could be well understood and appreciated. In short, the degree and manner of legal codification is not only an important aspect of law, but an exceedingly complex one. As a subject, it accordingly warrants an examination that is both in depth and wide-ranging. Up to now, no such enterprise had ever been undertaken.