Calibre (epub reader) install totally hosed my desktop

So I installed "Calibre" -- the epub reader -- on my Xenial drive and noticed right away that the icons on my top-panel & my desktop were suddenly all-white with a red "X" on them.

I re-booted, and the login screen was black (background image totally not there), but the username & password boxes still appeared, so at least I could log in.

The second I was logged in, although I could see that my startup programs had loaded, instantly the entire screen on both my monitors did this whole BLINK-BLINK-BLINK-BLINK thing and just kept up like that. So I can't use my 16.04 system and am posting this from my 14.04 drive.

I installed Calibre according to the instructions on its download page here. The command used was this:

sudo -v && wget -nv -O- https://raw.githubusercontent.com/kovidgoyal/calibre/master/setup/linux-installer.py | sudo python -c "import sys; main=lambda:sys.stderr.write('Download failedn'); exec(sys.stdin.read()); main()"

On the download page, below the install command, it says:

"You must have xdg-utils, wget and python ≥ 2.6 installed on your system before ruing the installer."

Since I have python 3.5 installed (and xdg-utls and wget), I didn't anticipate a problem. However, lower down on the page (I later saw), it says that one of Calibre's dependencies is "python 2.7.9 not 3.x." I don't have python 2, and whether that has anything to do with the desktop problem, I don't know.

I just know that I have to get 16.04 working asap.

Can anyone suggest what steps I should take to recover a functioning desktop?