Character mistake: At the end of chapter 16, Wade describes Columbus, Ohio as looking like Oz at the end of the yellow brick road. However Oz is the name of the world. It was the emerald city that was at the end of the yellow brick road.
Character mistake: It says 'Evie and Lottie said they tried to come round earlier but no-one answered'. It's supposed to be Evie and Amber, as it's Megan talking to Lottie.
Character mistake: Ch. 21: When Rocky tells Grace he blew the scabs off his wounds, he calls it a "black substance." But Grace never said it was black, and we know from when they get the first astrophage sample (Ch. 17) that Rocky doesn't understand "black" and "white." Even if Grace did explain what black is, offscreen so to speak, neither of them would know that Rocky's scabs later would be black. They never talked about it before (and if they had, Grace would have known not to mess with it).
Character mistake: In Ch 14, Langdon muses on hatha yoga as an ancient Buddhist art. Yoga originated in the Rig Vedas, an ancient Sanskrit text, and predates Buddhism by around 2,000 years.
Character mistake: In Chapter 62, Dayna Jurgens is talking to Randall Flagg. Flagg states that he has no intention of going to war, saying that "If humanity continues, let our grandfathers fight it out". He even repeats it; "Or their grandfathers". What Flagg must mean to say, is that their grandCHILDREN could fight it out.