While you are right, Michael, read on:
Depending on how thoroughly the two parties activated a book or how specific their purposes, it is possible that when you listen to their conversations about the book you would wonder whether they PhotoRead the same book. They may even wonder.
It could be like someone describing their experiences at the Mall of America. Someone's description could revolve around the Camp Snoopy amusement park, another's could revolve around 3.3 indoor miles of specialty shops, another's could revolve around the restaurants, and so on. Their conversations would converge, diverge, converge, diverge, and everything in between.