My wife just ran across a book called "In Character: Actors Acting" (just published this month). She found it an amazing piece of work and had to show me. I agree, it's the best book on facial expressions that I have seen.
As good as other facial expression books have been in the past, my one complaint with all of them has been that they don't feel genuine. They aren't real expressions. It's people off the street approximating what an angry or surprised look is. They also don't take into consideration body language. (I guess that's two complaints - sorry I miscounted.)
Where this book has the advantage over the others, is that the photos are of trained actors: Rosie Perez, Hume Cronyn, James Cromwell, Jason Alexander, to name a few. And the expressions are set up more like scenes. The actor wasn't told, "Look angry! Now infuriated!! Okay, now give me bashful." Instead the director said, "You are a man who has just been told he has inoperable cancer." or "You are a devoted father watching your handicapped daughter receive her high-school diploma." The results are incredible.
If you draw or animate, I really recommend you get this book. It is an invaluable resource. If you hate it, blame me for recommending it. If you love it, thank my wife for pointing it out to me.