As a professional networking software tester I have read atleast parts of most of the network programming books out there, andthis is the best of them so far. As previously mentioned the authors concentrate primarily on Winsock and mostly on C/C++ (as any serious network programmer should in both cases). Since this book does cover so many subjects though, some of the more peripheral subjects are mentioned relatively briefly, but hey, that's what SDK's are for. Concentrating on the main subject the authors do a great job of explaining Winsock and its application. I was particularly impressed by the comprehensive way in which they covered the differences between protocols, and between operating systems. It was also impressive (especially for an MSPress book) that they point out all the idiosyncracies and occasional bugs in the different implementations of Winsock. Obviously this book is intended for at least an intermediately skilled programmer, but should work well as a reference and an introduction to new topics (such as QOS, multicasting, and LSP's) to even more experienced coders.
To allay the conspiracy fears of those Linux people out there, I am not affiliated in any way with Microsoft Corporation or MSPress.