The format of the book is effective in that it allows one to follow the connections between various design rules/patterns that might otherwise not be obvious. The use of these "links" within the book could have been a source of inspiration for web designers. This book will appeal just as much to the lay person as it does to the legions of architectural professionals who use it as a guide on a frequent basis.
It's also pretty clear what Alexander values in design: community, sprituality, connection, nature, growth, and beauty. But after reading through a lot of these patterns, I can't help but agree with him. I hope that designers of all substances and forms will read this book and take up and continue evolving his ideas.
If you are an urban or rural planner or a computer software designer wishing to learn the basic principles of good design, then I would highly recommend that you get "Permaculture, a designers manual" first and "A pattern language" afterwards. If you are just a website designer especially someone who builds virtual communities then I would recommend you get "A pattern language" first and "Permaculture, a designers manual" afterwards. Newsflash; "Permaculture, a designers manual" is no longer for sale on Yahoo as of August of 2001, this book can only be obtained over the web through its publishers "Tagari.com.au".