I just finished his new book "The Art of the Start." I found it direct and informative. If you buy the book through his site, you get a nifty SanDisk 128MB USB Flash Drive.
Guy is the managing director of Garage Technology Ventures and cut his teeth at Apple in the early days and was a participant in the "Macintosh cult." He has been involved to varying degrees with several successful ventures including istockphoto.com, Tripwire and IP3 Networks which I think is a competitor of Aria Systems but they seem to concentrate on IP services.