Though its a few months before this book becomes generally availible (it will be April 6th according to Amazon), I wrote a side-bar for Brian Komar's next book "Windows Server 2008 PKI and Certificate Security", if this is the sort of thing that interests you consider pre-ordering the book, you will save some money and be one of the first to get the title.
Brian has given good coverage to some of the many improvements in Microsoft's PKI technologies that made it into Windows Server 2008, including the new OCSP server, certificate and key roaming and enrollment.