Windows System Programming, 3rd Edition by Johnson M. Hart is the sort of book that you might not need, but if you do need it, you need it bad. It is a C++ oriented book that goes into the details of all the Win32 details that you might ever need. It covers things like Thread Synchronization, Memory Mapped Files, Exception Handling, Interprocess Communications and Services. There is also a section on Win64.
Given that many folks in the Windows world are migrating to the .NET framework, which masks some of the Win32 details, as I said, you may not need this book. However, if you need to wring out the last little bit of performance, or especially if you need to venture into areas not well covered by the .NET Framework (such as Security), this is an excellent book to have nearby.
In the interest of full disclosure, I was one of a number of tech editors on this book. The tech edit process on this book was amazingly thorough, with multiple revisions reviewed by a number of tech editors. The end result is a very cool book for folks who need to get the most out of Win32.
Read: Book Review: Windows System Programming 3rd Edition, by Johnson M. Hart