Well, the rhyme has been interpreted to be referencing the plague, but there are some problems with that; the earliest version of the rhyme reported is 1790, with it being first printed in 1881. While that doesn't mean that original forms are about the plague, the language of the earlier versions doesn't hew particularly closely to the modern version, and the lines that people commonly interpret to be about the plague - the sneezing and reference to the 'pocket full of posies' (a tenuous link in any case) - are not present in all the earlier versions of the song. A version printed in 1883, but reportedly from the 1790s in Boston, has the lines 'a bottle full of posy/all the girls in our town/ring for little Josie'.

A final nail in the coffin is that the plague interpretation didn't appear until the mid-twentieth century, some 300-odd years after the fact. Before then, no link is drawn.

I can't provide a full review but I purchased a copy of this book last year and couldn't make it through the first chapter before I gave up on it. In establishing the background for the Black Death he played pretty fast and loose with his facts and showed a really strong bias from very early on. He was going pretty full-on for a 'The Middle Ages were Barbaric and Backwards' approach with no room for nuance or discussion, if I'm remembering it correctly. I gave up pretty quickly because I definitely felt like I wasn't going to get a fair or well reasoned account of the Black Death based on how he handled setting the scene.

Unfortunately, as I mentioned I didn't read the whole thing and I'm not an expert on the Black Death (I had bought the book to learn more) so I can't provide a more detailed critique than that.