The quiet reader can be having the busiest conversation in the room.

Reading looks like the absence of activity and is nothing of the kind. Somebody sitting still with a book is arguing, agreeing, being persuaded and objecting at speed, while the room registers all of that as doing nothing. Stillness is a poor measure of what is happening in a person. Attention has no outward volume.

Be careful about interrupting quiet people on the assumption that they are free. And when your own week has no visible output, remember that reading and thinking are work which happens to look like rest. Not everything productive announces itself across a room.