Not a fan of the new look. If you’re in the same boat, plug:
about:config
into your URL bar, and search for:
browser.nova.enabled
Toggle it to false using the button to the right.
There are functional changes that Nova also introduced: this won’t effect those - only the aesthetic.
Thanks for this. I was open minded until I saw it for myself. Your post fixed a problem I didn’t know I was about to have.