The Artist's Complete Guide to Facial Expression

It's a very cool book with a great systematic approach as a reference for expressions. My only quibble with it is that the green overlaid color is on some pages slightly out of alignment in my copy. It's only a few millimeters but that kind of printing fault shouldn't happen in an art book. It's nowhere bad enough to impede usefulness or legibility, though.

Extremely detailed, the book is difficult but provides clear, if lengthy, instruction on modelling facial exdpressions--just like the title says, as it turns out.