I was looking at a Spanish language textbook that was left under my desk by the previous AET, and also a Chinese language textbook I had bought in China. I thought back to highschool and university, and recalled what the books looked like back then. Yep, they were pretty heavy and thick.
Then I look at my kids' textbooks, which are about 1/3 the thickness. They also have "workbooks", but they are 1/5 the size of the textbooks used in the U.S. Half the time, I don't really understand the target grammar in the textbook. The vocabulary list seems quite random (and sparse) as well.