In the Jaran novels, Elliott uses the very different characters of Tess and Jiroannes to highlight the culture from both perspectives. In The Law of Becoming , Jiroannes' culture-blindness adds an extra layer, since his misunderstanding of jaran culture also reveals a great deal about his birth culture through the assumptions he makes, the way he dresses and has himself cared for, and through the people he surrounds himself with and how he relates to them. Such characters should also be used with caution, however. Otherwise they become so creaky that one can hear the gears turning behind the scenery. Determining which details a character should observe is as important as determining the observation character in the first place.
Words are precious, even in a huge tome.
These details matter, because they reveal something about cultural expectations, assumptions, the level of technology, the political system, and so on. Similarly, characters should observe appropriate details about other characters. One such peeve relates to the economy of speculative worlds. I can only get so far in a story once I've realized that the inns work as grocery stores, the marketplaces as malls, and the horses as trucks. I find this tiresome because all I have to do is pick up a newspaper to discover that human beings are perfectly capable of inflicting all kinds of damage on their fellow human beings for a variety of reasons, some seemingly grand, some insane, and all too many banal, greedy, or selfish.