getYesod function has been replaced with getSubYesod in code snippets, but the text stil refers to getYesod (e.g. "The next call to getYesod is not lifted."). It would be nice if there were explanation about getSubYesod, especially given it is not covered in subsite book section at all.
I also think that the example won't compile with that replacement as it is, though it may be me doing something wrong.