Here's a tip for U.S. art teachers who are about to start the fall term.
Prices on Amazon.com are always low, but they fluctuate up and down by as much as 25%. Color and Light: A Guide for the Realist Painter is at the lowest price that I've ever seen it. It's a whole art education for the price of a chicken-avocado wrap.
Whether you get a single teacher's copy for yourself or a whole set to use as a class textbook, this is a deal you might not want to miss.