What does Programming the Windows 95 API by Charles Petzold cover? Do you learn how to open and save files?

Ah, the Petzold book. This book is pretty much the end all of learning the Win32 API. It starts from the very beginning and works its way up through more advanced concepts, such as File IO.

I recommend this book to anyone doing anything in Windows. It''s really nice to know the API when working with DirectX.
It''s also nice to know if you use MFC since MFC is just a class wrapper for the API.