That is the frustrating thing... I am currently using Linux and it is taking me a while to work out how to get windows products that would do the conversion job well like Irfanview or Format Factory to work under this operating system.
Even very old versions of photoshop allowed you to save image files where you could change the format type and resolution and image size and it would show the file size so you could take one page and have four versions of it on screen each taking up a quarter of the screen with the original image and then three other available alternatives so you might have the original jpg in the top left and in the top right you might have a lower quality jpg setting, while bottom left you could have gif format and bottom right maybe tiff file format and you could see each image side by side zoomed in on text or images on the same page so you could compare the quality directly with the original. It would also display the file size for each format so if there is a huge reduction in file size but everything is still clear you could base your choice on file size, or if the picture is not good enough you can change the parameters... most jpgs have millions of colours per pixel which means 16 to 24 bits per pixel depending on the image quality.. with a gif you might only need 256 colours... which means 8 bits per pixel would be fine.
It is something I have been meaning to do... work out more useful tools in Linux that I used to use a lot when I was using Windows or even Workbench. With Irfanview there are batch processing scripts... you could just drag all the pages into the process list and choose convert to gif and then click start.
I remember doing a project where I was working with documents someone else had scanned where each page was 3-4 megabytes like these ones and it was a real pain in the ass because it was a few years ago and the computer I was using was much slower than this one. It took days to download ten pages on dial up, and I couldn't work with more than three pages open at any one time... jpg is a compression format so when you have it open it takes up orders of magnitude more space in computer memory... I opened one of the pages you posted in the Linux equivalent of Photoshop called GIMP and the file size open was over 100 megabytes and things didn't move fast or smooth. I decided back then to convert them to gif format files to make them easier to use and work with... do you know how many floppy disks you need for a 4 megabyte file and what a pain in the ass a file splitting programme is to split the files to fit them on a 1.4MB floppy...
Anyway, after converting to gif, the files were less than 300K each and loaded real fast and I could still use optical character recognition software to convert it into editable text that I could then search and edit... it made everything so much easier.
The person who scanned it didn't know what I was using it for so they scanned at 600dpi to get every single detail, but most of the time legible text is all you need... which means 300dpi is good enough without being too bloated a file for OCR.
Anyway sorry for going on about this... thank you again for posting the book.