This is the latest available. Is there any chance that an update will become available ? (Its been over 20 years…)
The Repair part is what prevents another edition from being done, to be honest. Even though there is still a lot of repair information that is applicable in that book, repair has changed a lot and every year we have to come up with another tool or technique to deal with some new thing. The fitting and design basics do not change and are still applicable. The Golf Club Fitting and Performance book published in 2011 carries these principles and provides you with more detail on design and fitting, but does not cover repair. Also, there is a lot of content on repair on the internet and it is easier, and cheaper, to create video content on repair and assembly than putting it into a book that can be dated as soon as it is printed. So, at least for now, no plans for an update on the Repair part of the book.