<p>Our testers are in the process of evaluating Visual Studio Team System 2008 Test Edition. As they are unfamiliar with the use of Visual Studio, I would like to give them as much help as I can.</p>

<p>I have had a look on Amazon for books on the Test edition of VS.Net, but there is only one VS.Net 2005 test edition book.</p>

<p>Does anyone know of any good books, or online training resources with a particular focus on the features of the Test Edition of Visual Studio Team System 2008?</p>

For someone evaluating features who isn't that familiar with Visual Studio, I'd recommend the videos from a few places:
"How Do I?" Videos for Team System
ASP.net's Learn section
Video tutorials at TeamSystemRocks.com
Plenty of videos between those sites on the various VSTS Test Edition features.  Note that many are about VS2005, but the fundamental concepts don't change when moving to 2008.
Once they get the basic features, here's a summary of
What's New in VS2008 Test Edition
.
See also:
VSTS 2008 Test Edition Home
(BTW, there's a link to a trial VPC w/TFS & VSTS Suite on the right-hand side)
Visual Studio 2008 Training Kit
- Not a lot on VSTS in here, but there are a few demos and resources that touch on the Test features, and it's a good general resource to have, anyway.