Magazines are going to be a much more difficult thing for size than books would be. High-resolution colour scans take up an enormous amount of space.
When scanning books, most people tend to convert their scans to binarized form - where there are only two colours, pure black and pure white. It works decently for books that contain only text, though it does mean you lose the original book's appearance. I wouldn't use it for historic books. Depending on the compression you use, you could expect results well under 10MB for 100 black and white pages. A 70-page book PDF I compressed at my previous employer using lossy JBIG2 came out to under 6MB, with OCR embedded - smaller than that with no OCR.
Here's a link to the book in question.
For high resolution colour images, there's really not much you can do to help reduce file sizes except to use a more efficient compression - for instance, JPEG2000. Losslessly-compressed high res colour images will always take up large amounts of space and there's not much that can be done; it's a difference between "huge" and "slightly less huge".
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.
