Dumbledore tells Harry at the end that Lord Voldemort is the last remaining ancestor of Salazar Slytherin. But ancestors are in the past - he means Voldemort is the last descendant of Salazar Slytherin. Not a mistake Dumbledore would have made. (Corrected in later printings.)

About two thirds of the way through Ch. 1, Sookie serves a pitcher of beer to her brother Jason's boss, Shirley Hunter. But in the previous book, Dead to the World, Jason's boss Shirley's last name was Hennessey (Ch. 3).

In Chapter 4, Garraty thinks about Jan and her long, dark hair. Later, in Chapter 6, he once again thinks of her, this time with her long, blonde hair.

When Fitz and the Fool have swapped bodies, after Fitz repairs the Fool's body, he "uses their combined strength" to lift himself - in the Fool's body - up to touch foreheads with his own body. Then he and the Fool go into their proper bodies. However, Fitz then says that he "straightened up and looked down at the Fool in my arms." This isn't possible, because the Fool's body had moved upward, but Fitz's hadn't moved downward. Yet the Fool doesn't move, Fitz does.

In the previous book, Dark Assassin, Monk goes through Durban's notes and finds the only case of his which "remained a mystery" (Ch. 7). The case Monk reopens in the next book, Execution Dock, is also repeatedly referred to as "the one case Durban had not solved" (e.g., Ch. 1 and Ch. 5). The mistake is that there is no way these are the same case. The one from Dark Assassin involves the murder of a 40-year-old barber named Roger Thorwood; the one from Execution Dock is the sexual abuse and murder of a boy named Walter Figgis, by a man named Jericho Phillips. None of the suspects, victims, or witnesses in the two cases overlap at all. Of course Durban could have worked on both cases – but they can't both be the one single case he never solved. And if they are both unfinished, then it is wrong to say (as the author does repeatedly in Execution Dock) that there is only one case Durban didn't close. (It also can't be a character mistake on Monk's part, since he knows about both cases).