They look at everything on the screen and try to tell us what is coming in the video game.
The music alone guarantees I will play the game.
The books note that Indy is also studying Ancient Circles and Forbidden Stones. The tagline on the Forbidden Stones book reads "A treatise on corrupted jewels and the essence of ancient curses," which provides some further detail on what Indy might be looking for in Mesopotamia.
Then in the bottom left corner, we can see a tiny note written by Indy, which says "Pyramids Giza Necropolis," referring to the Giza complex of pyramids in Cairo, the last remaining ancient wonder of the world. The yellow pages north of this note offer a sketch of the Peruvian "Forbidden Idol" retrieved in Raiders and a drawing of a Ziggurat, a common structure found in ancient Mesopotamia. Indy has written "Ziggurat Clue?" nearby, so he's definitely studying it. Whether he will visit any of these places in the game is still up in the air, but it's good food for thought regardless.