I found myself having no problem reading it, knowing bits of set theory I had taught myself beforehand, but I have to admit I would have been confused otherwise

I found myself having no problem reading it, knowing bits of set theory I had taught myself beforehand, but I have to admit I would have been confused otherwise. Given the authors have the book open-sourced and that this looks like it's still a draft, it might be a good idea to forward your criticism to the authors. I'm sure they'd appreciate it.