As a generalization I have to disagree, at least in America for high-school subjects. I looked at both the math and biology texts from recent years. The math texts were written by people who didn't understand math, and the biology text was so focussed on the No Child Left Behind Act requirements that it was rubbish. (Also look for Richard Feynmann's experience reviewing textbooks). Undoubtedly there are good textbooks out there, but they are just as much in need of review and recommendation as non-textbooks.