It's somewhat common for me to read in my dreams but I can barely see the text for a second (it is decipherable though): My perspective instantly shifts "inside" the book, or rather the story it's telling becomes the new focus of my dream and I can visualize it just fine (sometimes I don't even come back to the previous world, my dream is now about this new story). Same thing if i'm playing a game: for a second I see the frame of the monitor on the borders of my vision but quickly it disappears and all I see is the content of the screen. Sometimes it keeps looking like the game (like, Civ always looks like Civ) and others it becomes more flexible and cinematographic I guess, a new story that can go anywhere.