With this fourth edition, the time is right to separate out the different forms of electronic signature, giving each a separate chapter. I anticipate that this approach will enable the reader to have a better understanding of the different forms in which an electronic signature can be manifest. The case law on the topic has increased – in fact it has increased to such an extent that I have not been able to incorporate as many cases in this text as I have discovered after cursory searches in electronic search engines. If I have missed a particularly important case, please let me know. I have begun to prefer citing case law from appellate courts. I have also removed the extensive list of legislation on the basis that I maintain a table of world legislation that is updated and published in the Digital Evidence and Electronic Signature Law Review occasionally. This list in turn now relies on lawyers and legal scholars from across the world to help keep it up-to-date. This leads me on to consider the purpose and structure of this book. A number of issues arise, such as whether the book should be as comprehensive as possible, or a more selective approach might be considered; whether to include examples from as many jurisdictions as possible, or to restrict the citing of examples. In addition, the question also arises as to how individual chapters for each type of electronic signature is structured – that is, whether a country by country analysis is appropriate, or if the analysis by legal topic is more helpful, together with a breakdown by jurisdiction.