I bought Don Syme's Expert F# book a couple of weeks ago. This is the definitive guide to a language that's going to become an officially supported part of the Visual Studio family in the coming year or so. Amazon UK don't seem to have it yet so I bought from Computer Manuals and received a very speedy service.
I've seen quite a few rave reviews of Advanced Windows Debugging including from Raymond Chen and also from Mike. I think this one will make my wish list. :)