Interesting side note: the book itself is copyright Cambridge University Press. The authors have a free version accessible online and a promise to keep it that

Interesting side note: the book itself is copyright Cambridge University Press. The authors have a free version accessible online and a promise to keep it that way, but seemingly no open license on it. I don't blame them, probably not much choice to get a decent print run, but it's an interesting display of how pervasive copyright is.