Sort by change date
Sorting by the modification date may be useful if you “pick up” all the images, i.e. edit in the order they should appear in the book.
Often all images are adjusted in e.g. tonal values, exposure, clipping, saturation, etc.
If images are edited and saved in the correct order, i.e. “page by page”, a sort by modification date may work.
If you are usinging a tool like Adobe Lightroom and then save the selected images into a new folder, the modification date may be used for sorting purposes also.
But a better approach is giving those images new names with an image number in the correct format, i.e. with leading “0000”. Then an alphabetical sort can be used.