The target audience for this book is primarily developers building software for Windows Vista. There are some design considerations in the book too, so designers and architects will get some benefit. Note however, that this book is very code-heavy.
It is also assumed you have some knowledge of the Windows authentication and authorization system. While some background information is provided in this book, it is assumed the reader knows how objects are protected in Windows. If you do not, you should read a book such as Windows Internals Fourth Edition, by Mark Russinovich and David Solomon (Microsoft Press 2005).