First off, due to a confusion at Amazon, the other reader reviews shown with earlier dates than this one are not for this book but for an earlier book by the same author with the similar name "High Performance Sailing". This book "HighER Performance Sailing" was published June 1 2009.
Frank Bethwaite refers to the older book as HPS-1 and this book as HPS-2. This book is not a revision of HPS-1 but really a completely new book that picks up from, and in many cases revises, the information set out in HPS-1. In certain places Bethwaite gives a brief recap of information from the earlier book and then refers the reader to it for more detail, but you can profitably read this book without ever having seen HPS-1.
HPS-1 was a brilliant book whose audience was reduced by a very eccentric organization and a very awkward writing style. Where a conventional book would try to lead you carefully from topic to topic while making sure that you haven't been left behind, HPS-1 doesn't. It reads more like the personal notebook of a mad scientist whose areas of study are the wind, the evolution of performance yacht design, and racing strategy. There was a huge amount of valuable, practical knowledge in this book that was new and hadn't been written before, but because of its very awkward exposition it was hard to extract. I had to read HPS-1 twice to get the benefit of it --- the first time to get an idea of what points he was trying to make, and a second time to decode the details. But it was well worth the effort. The discussions about how the wind works, in particular, are far more sophisticated and useful than anything else you'll find in the sailing or meteorological literature.
Where most of the information in HPS-1 was relevant to racing in any kind of boat. This new book is much more focused on the new and unique properties of modern skiffs and skiff-like boats that can sail faster than the wind. The writing style of this book seems to be better to me but perhaps only because I've become acclimated from the earlier one. The organization of this book is perhaps even more eccentric than the earlier book and jumps fairly randomly between various topics that the author finds interesting. There is also a huge amount of repetition. A good editor could have made this a much more appealing read.
But there are some gems of practical sailing knowledge in this book that I don't think you'll you won't find anywhere else. There is also a lot of historical information that won't help you sail faster but you will probably find surprising and interesting if you have an interest in the history of sailboat racing.