Ok, I think this is as small as I can make it. I've deleted all the Thumbs.db, rars, zips, and exes. Everything else is intact (though various readme.txts have been moved to more appropriate subdirectories).
619340 -rw-r--r-- 1 root root 634198613 2013-07-21 13:21 /tmp/nonfic.7z
So, 619.3 Meg in a 7z file for all the non-fiction Railways here.
Up to now, I have not paid that much attention to the Trains, but I may be able to do the same for them today and/or tomorrow.