As the book is called “Helvetica by Eric Gill” I am going to look into the differences between the two fonts. I will break down some characters and really analyse them, their pro’s, their con’s and their successful uses.
An idea that approached me was to, on the front cover, overlay the words “Helvetica by Eric Gill” twice. Once with Helvetica and, below it, with Gill Sans.
This might clear up any unnecessary confusion in the witty title.