Following up on this note with a smaller, funnier point I didn’t have room for there: complaining in the margin is not a modern habit invented by online reviews. Medieval scribes and early readers left an enormous, well-documented record of grumbling directly onto the page they were working on or reading.
The famous scribal colophons include lines like ‘thin ink, bad parchment, cold fingers, I hope whoever reads this appreciates what it cost me,’ written at the end of a hand-copied manuscript that took months. Readers annotating printed books left their own version a bit later — arguments in the margin, corrections to the printer’s errors, the occasional flatly rude aside about the author that the author, mercifully, never saw.
None of it was written for an audience beyond, at most, the next owner of that specific physical copy. Which is what makes it different from a modern review, and closer in spirit to what a lot of this site actually is: notes made because the making of them was useful to the maker, publication being a secondary, almost incidental fact about where the notes ended up.