Sorry for not getting back to you earlier.
Would you both prefer a quick right click (2 finger tap) to be roll back a page, or would you like a single tap exclusively on the far left side of the page to be the go back shortcut?
Im partial to the far left tap being go back, simply because that is how im used to touchscreen readers functioning everywhere else, but some people seem to thing that right clicking is a better option.
I actually would adapt to whatever you implement. Still, tapping on the far left would come more naturally to me as well.
Now, thinking about it, I would actually love to just have two big buttons on the lower left and right corner. Maybe looking like "<" and ">" in the small navigation bar that is there now. That way, I could tap one of those any time in full screen mode to go back an forth. Especially while viewing a page zoomed in that would be useful.
Failing that, I would prefer the tap on the far left and the far right to jump 1 page back/ahead.
Thanks for keeping the conversation alive!