I'm having a hard time getting my photos to fit appropriately in the cells. Regardless of the size of the image I almost always get an exclamation point warning.
An "exclamation point warning" indicates that your print resolution (pixels per inch) may not be sufficient to print in the book at "best quality", it does not indicate "fit"..
Work with your full-size images. Do not resize your images by exporting. Do not crop- the same can be achieved in the Book module.You can zoom in on the book page image to effectively crop. You can make images "Fit" or "Fill" any size image cell.