I don't use textbooks to study, but my general studies have garnered a sense of respect for the general politeness found in the Japanese language. While English text leaves a lot to the reader's interpretation, Japanese text has its own pronounced level of politeness, from extreme courtesy to blunt (or outright rude) speech, all without relying on audible tones as a communication vector. (I primarily play Japanese video games for exposure purposes, and the degree of courtesy, or lack thereof, tends to be jarring in comparison to the neutral English dialogue, in a good way of course.) Just a thought.