First draft of the new edition of WAHH is now completed. 30% of the content in the second edition is either completely new or extensively revised. Most of the material in the first edition remains valid and current today. The bulk of what constitutes our accumulated wisdom has evolved slowly over many years, and would have been distinctively recognizable to practitioners working a decade or more ago. Chapters 9 and 10 have been reorganized to create more manageable and logical arrangement of chapters and a more logical arrangement.
Source: https://thehackernews.com/2011/05/preview-web-app-hackers-handbook-2nd.html