During my sophomore year at Cal Poly, I decided that I wanted to learn about threads, synchronization techniques and other topics associated modern operating systems.  Windows 95 had made its debut (yes, it is not a modern OS, but I didn't know that at the time!) and I had heard about Windows NT, but had never seen or used it.  Since I had Win95 on my machine at home, I decided that I would go to the bookstore and buy a book on threading. 

Well, needless to say there was not a book that was dedicated to threading, but I found a couple of books on Windows programming that included threading as topics.  It came down to 2 books, Jeffrey Richter's "Advanced Windows for Win95 and NT" (with Napoleon on the cover) and some other book.  I obviously picked Richter's book ;), although now it is called "Windows via C/C++."

This book was, and still is, awesome.  I have both the original and new editions.  Great detail, very easy to read and met it my needs perfectly (unlike "Inside OLE" by Kraig Brockschmidt which was full of information, I just could not stay awake reading it :) ).  IMHO, it successfully started me down the road to becoming a well rounded developer and I think it helped in getting my foot in the door at Microsoft.  I have even had the pleasure of letting Jeff know personally what a great book it is and how it shaped me for years to com.