Load into the tower courtyard and open your ghost. Turn to the left and you will see two large blue crates and some orange containers. Walk towards them with your ghost open and a weird crosshair will activate. If you then turn to face the safety nets where the robot is waving glow sticks — stand next to him on the right and look down. THERE IS A GHOST zapping around uber the grates. I’ve tried to reach him but I can’t. Edit: Found a way to the ghost by dropping onto the metal beams below the safety nets. The ghost is there with a bunch of books and bottles. Putting your weird crosshair onto the book makes a cube appear and the book flash with blue lines. When your ghost is closed the sound disappears and there is no flashing. Edit 2: Checked again today and the book was scannable but the hovering ghost and weird crosshair was gone.
You can let your ghost scan that book and it tells a little something about the people of the tower. Those spots with books or pads are spread across the tower waiting to be found.