Looks like the old paths for grabbing the images are not working any more. I also couldn't seem to get the CURL to work with my cookie but after some digging I was able to get the following working as the grabber:
wget --load-cookies cookies.txt https://jigsaw.gilmoreglobal.com/books/${isbn}/images/${page} -O ${isbn}/${page}.jpg
Looks like the old paths for grabbing the images are not working any more. I also couldn't seem to get the CURL to work with my cookie but after some digging I was able to get the following working as the grabber:
wget --load-cookies cookies.txt https://jigsaw.gilmoreglobal.com/books/${isbn}/images/${page} -O ${isbn}/${page}.jpg