This is a short book. Amazon count 204 pages, but I reckon that if you only count pages with stuff to read on, there aren't much over 100 pages. So I was a little amused when the authors stated that they expected you to read the book in a week or two. 3 days at a push more like it.
So, it's clearly not a subject that is amenable to inspire a 1000 page tome. There are quite a few cartoons which, depending on your point of view, pad out the pages or add some levity.
I felt that the authors were struggling to stretch the idea to fill a book. The advice on 'plain English' for comments and variable names is sound. I wasn't sure sometimes whether the ideas about refactoring were 'readability' issues or just simply better code.
The example code leans towards Google Javascript. That made me think a bit about Spinellis' "Code Reading" which, though coming at the problem from the other direction (how to read code rather than how to write code that can be read), does have fairly broad coverage. I don't think that you can have a checklist for the creativity required for readability, but perhaps this book would have benefited from a few pearls of wisdom from a few revered programming gurus.