I have "Ratio: The Simple Codes Behind the Craft of Everyday Cooking" and was unimpressed. The idea of thinking in ratios is useful, but not the oversimplification to a few prototypes. You could look at a recipe as something with a whole bunch of ratios and valid ranges, and document the effects of variation and so on. It would be a much bigger book and not "this little volume contains all the secrets to everything".
Edit: by the way, what is with the Amazon pricing? Hardcover is $25; "mass market paperback", new is $901! Not to mention, the featured hardcover price is noticeably more than the specific new hardcover price of $20.
On Food and Cooking is a fantastic book, by the way. A real classic that every food enthusiast should have on their shelf. I recommend the hardcover version.