I only see the option of exporting the entire book as individual jpgs. If I make a single change to a single page, to get the revised page as jpg I seem to have to export the entire book again. Is there an easier way to get the jpg of the updated page?
No, you cannot export a single page from Book Module.
However, you can try the following suggestion if you are making book with a smaller number of pages :
duplicate the book in Collections panel (right click > duplicate book) > then, choose the duplicate book > edit the required page and remove all the pages except from the one you want to be exported > choose export as Jpeg.
Nice workaround. thanks.