This isn't just a good way to multi-task the whole book-reading thing, but I also pay close attention to the narrator, especially the really good ones. A few years ago my gaming group at the time pointed out to me in a not-so-subtle way that all my NPC's tended to have the same voice: I'd squint up one eye and start talking vaguely like a pirate.
|Apparently every NPC in my games|
Again, this isn't ground-breaking innovation like some clever new way to do NPC write-ups, just some small ways I try to do things better. Hope it helps.