I tried to download the links when the topic was first posted, and got all the same issues as Hitch. I just tried now and the downloads work.
Although the robot math problems were annoying. (I was also able to get around many of them by just going Back/Forward in my browser. It gave me the same exact math question.) :P
PS. The font you use in your ebooks, Arsenal, is much too thin to read on screen. I had to bump up the zoom in Sigil and my eyes still hurt.
Also, some of your buttons here:
https://ebookfonts.uk/cgi-bin/ffdl.cgi?j=fb
link to the same exact files, even though they have different filenames.