Continuity mistake: In the scene where Bess, George and Nancy are talking about cowboys on the ranch, Bess mentions how Ned, Nancy's boyfriend, is going to be jealous, but this is book 5, and she doesn't meet Ned until book 7.
Factual error: The book is set in 1938, and features a Catalina PBY amphibious aircraft (fitted with retracting wheels so it can land on water and/or land). In 1938, the Catalina was only manufactured as a seaplane. It was not manufactured as an amphibian with wheels until 1941.
Continuity mistake: In the Seventh Stanza, part 2, Eddie and Roland are involved in a gunfight alongside two civilians, one (later identified as John Cullum) who is wearing a flannel shirt, and Chip, the store owner. But at one point, two men come around on Eddie's side of the store, also wearing flannel shirts, that are described as "unlike Chip's shirt, they seemed brand-new". Chip is not wearing the flannel, John is.
Continuity mistake: When Harry is viewing Snape's memories, he witnesses a scene on Platform 9 3/4 between his mother and aunt Pentunia, in which Petunia tugs her hand out of Lily's grasp. Her hand is then back in Lily's and she tugs it out again.
Continuity mistake: 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.
Continuity mistake: The torturer is described as being naked to the waist but shortly afterwards as having blood on his shirt.
Continuity mistake: In the second book it says that Artemis' father's last memory was waving goodbye to his family but in one of the diary extracts, when Artemis is at the hospital with his father, his father talks about his time as a prisoner, which he shouldn't be able to remember.
Continuity mistake: When Mulch helps Holly and Artemis from the trunk of the car, when they've gone back in time, it says that he burps. Yet in the first book it says that all dwarf wind is passed down, so Mulch is incapable of burping.
Continuity mistake: In chapter 17, where Huck first meets the Grangerford family, Col. Grangerford is described as "grey and about sixty". However, in the next chapter, the colonel is described in more detail, and his grey hairs are gone. Huck describes him as "clean-shaved, all over his thin face", and with hair "black and straight".
Continuity mistake: In Return of the Jedi (and every book taking place after) Luke Skywalker's lightsaber is green. However, when Luke is talking to Han in this book about what he must do while on the satellite, his saber is blue. Later on the author changes it back to the green saber.
Plot hole: When Phelan Kell is testing to become a Wolf Clan mechwarrior, his Dire Wolf's cockpit takes a hit from a Clan PPC. He continues to fight despite his cockpit now being in open air. In the Battletech universe, a cockpit hit from a Clan PPC is instant death.
Factual error: The author says that the real Scottish king, Macbeth, died in the year before the Battle of Hastings in 1066. But Macbeth actually died in 1057.
Continuity mistake: In Chapter 28, "Homecoming", Fitz falls asleep while drinking wine in his bath. When Chade enters and startles him awake, Fitz is still holding the neck of the wine bottle, which Chade catches before Fitz upends it. This means his hand with the bottle was outside of the tub. But only a page later, Fitz mentions that both his hands are wrinkled from being immersed in water for so long.
Continuity mistake: In chapter 13, the police have identified Pops as Austin Charles Bailey. While he is being questioned, the author refers to him as "Arthur Bailey".
Continuity mistake: When Graystripe and Firestar spy on the Tigerclan camp they name the cats in the clearing. Mudfur is among them but on the next page it mentions a lack of medicine cats. Mudfur is the medicine cat. As far as I know you can't unbecome a medicine cat.
Continuity mistake: In Mammoth Hunters, after Rydag died and Ayla was being the mog-ur, she gave Rydag "her totem" the cave lion, but in Plains of Passage she stated that his totem was the grey wolf.
Continuity mistake: Chapter 26, "Night Watch", Steward Third Class is introduced as Rosie McCullen. A few pages later in the next chapter, "Rosie", her name changes to Rosie McMahon. (First Edition, January 1988).
Factual error: In a paragraph at the beginning of the book (page 26 in my edition) where the author is describing the character Alice Austen, it is written "Austen was wearing a public health service uniform-pants and a short-sleeved khaki shirt with the gold oak leaf of a lieutenant commander". Gold oak leaf is Major, silver oak leaf is Lt. Commander.
Continuity mistake: In section 3 of the chapter called Bear and Bone, Eddie Dean reminisces about his dead sister Gloria. But in the previous book (The Drawing of the Three), Eddie's dead sister's name was Selina (Ch 3: Contact and Landing).
Continuity mistake: In the first book, Devil on My Back, Arbor is Rowan's brother, and she is teased because of Groundsel's interest in her (Chapter 4: Rowan). But in the sequel, The Dream Catcher, all of a sudden Groundsel is Rowan's brother, and Rowan says she had promised to marry Arbor (Chapter 9: The Sharing). The two male characters have been reversed.