Hard to tell what it may have been used for! It's about as mysterious as the antikythera mechanism, not in form but in complete lack of information about what it might have been. It's definitely from a strange culture, it doesn't seem to match anything else found in town or in any other ship, and its markings don't correspond to anything in this world.

The book is in an equally-inscrutable language. It's very clearly handwritten in a dark, thick ink. It reads right to left, drops down a line, and then reads left to right, and continues that way down to the bottom of the page. It then seems to do the same in reverse, climbing the page from left to right, then right to left, until it gets to the top.

Interspersed between the remaining pages of writing are a few pages with drawings done in the same dark ink. The drawings are:

-various cacti, recognizable from the desert around them
-a town, drawn from a slight distance away. One large building anchors the town at one end, and a row of buildings stretches out from either side. The large building is the Staywell Hotel.
-an inky sketch of three people's faces. They are all wearing western gear, and some of them are smiling. None of them are recognizable. All are labeled beneath, first in the flowery writing from the rest of the book, and then below that in smaller, different letters in a different hand, recognizable English words. The portraits are labeled José Burch, Sherman Navarro, and June (illegible last name).
-a drawing of a coyote standing on its hind legs
-a drawing of a long-legged jackrabbit with antlers growing from between its ears
-a page full of sketchy, inked eyes
-a view of the graveyard, with several gravestones and the old well in the background