My home desktop runs Zorin but I have no web access at home. I have an Android phone. Can I download an epub reader, transfer it to my desk computer and install it for Zorin?
calibre is a good epub reader but I don't know about the transferring part. You can install it using Synaptic.
You could use your phone as a hotspot and install an epub app from the Gnome software center on your desktop if you have a wireless card or dongle.
In addition to Calibre, I also use FB reader (FB stands for favorite book, not facebook). I discovered FB reader when I was trying out reader apps for my phone. That was the best one I tried. On the PC I still prefer Calibre.