I finished Les Xipéhuz. I was looking forward to strange extraterrestrials vs pre-historic humans and the first third or so didn't disappoint, but then we were unfortunately introduced to the hilariously anachronistic protagonist/narrator that felt like a XIX century gentleman observing and narrating things and not some intelligent man from tens of thousands of years ago. The technique to introduce his direct narration was clever (some professor's translation of pre-cuneiform tablets) but besides some metaphors and epithets, he sounded way too modern and his observation of the alien lifeforms were ridiculously precise and mathematical. This in turn turned the final battle with the Xipéhuz into something anticlimactic for me, because I would have preferred seeing a bunch of people with limited knowledge and power cooperate against a seemingly unbeatable enemy instead of one big brained guy using Reason™. But maybe it's just me. The Xipéhuz were very interesting anyway.