Continuity mistake: In Chapter 19, Wade describes the small efficiency apartment he has moved into, which used to be an average hotel room. He says at one point that the room "was basically a cube, about ten meters long on each side." A ten-meter cube is actually a really big room - that's over 32 feet on each side, including ceiling height. Then, just to confirm that this is indeed a mistake, later in the same chapter he refers to "my tiny one-room apartment."
Factual error: In the book Teabing is a die hard British patriot, yet he refers to the sport of soccer. NO Englishman would use the word soccer for the game of football. [People keep trying to correct this - you've really got to accept it. It's nothing to do with Teabing being older - soccer may have been used in the very early days of the game, but the governing body of the sport in the UK is the Football Association, formed in 1863, demonstrating how that was the accepted word for the sport even then (otherwise it would be the Soccer Association). Likewise the international governing body, FIFA (Fédération Internationale de Football Association), formed in 1904 - no mention of the word soccer there either. And it won't be him changing it for Langdon's benefit, considering a) Langdon's intelligent enough to know what he means, and b) he's so determinedly English about everything else. This site is run by a Brit, and it's not getting changed. :-)]
Continuity mistake: 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.)
Continuity mistake: During Priori Incantatem, Voldemort's victims come out in reverse order. However, James comes out before Lily. He should come out last, because he was killed before Lily. (Corrected in later versions of the book).
Factual error: In chapter 21 Vittoria states that "everything has an opposite. Protons have electrons." Protons and electrons are NOT opposites. The opposite of a proton is an antiproton, the opposite of an electron an antielectron (or positron). Other than having opposite charges, a proton is completely different from an electron, ie. a proton is a hadron made from 3 quarks, Up Up Down, making it a baryon. An electron is a first generation lepton and is a fundamental particle. As a physicist, Vittoria wouldn't make this mistake.
Continuity mistake: Harry buys the book "One Thousand Magical Herbs and Fungi", but later, the title changes to "One Hundred Magical Herbs and Fungi".
Factual error: In Chapter 5, Koontz explains how Grandma Rowena started smacking her lips while eating, at the age of 75. He then says this same event happened "halfway between her seventh and eighth decades". But at 75, she is actually halfway between her eighth and ninth decades (or, if you prefer, halfway through her eighth decade) - much like the 1700s are the 18th century, not the 17th.
Factual error: When Arnie and Leigh gives the hitchhiker a ride, on page 265 (Chapter 34), it says that the hitchhiker opened Christine's rear door. But Plymouth Furies of that era had only two doors.
Continuity mistake: Eddie's broken arm changes around, sometimes it's the left arm that's broken, sometimes it's the right.
Continuity mistake: The pickup truck with the painting of the Gypsy woman and the unicorn in Chapter 6 changes into a VW microbus in Chapter 18.
Continuity mistake: At the beginning of the book Meggie mourns leaving the farmhouse she has lived in for just under a year, but at the end of the book she suddenly remembers having lived there for the past several years.
Plot hole: When Julius is going after Pompey to Asia Minor and he reaches the harbor in Greece he tries to talk to the sailors but they don't speak Latin. So he asks Adán to translate for him, but he is unable to since he hasn't learned Greek yet. But Julius is fluent in Greek himself, he was taught as a boy and uses the language on several occasions throughout the series, including in this book. Why couldn't he just talk to the sailors in Greek himself?
Continuity mistake: In the chapter entitled Smooth Criminal, Reed is asked by the Billing's Girls to steal a physics test and that she has 15 minutes to do it. Early in the chapter she states that after glancing at her watch she had already wasted 4 minutes but at the end of the chapter she states that she wished she'd had time to put on a watch as she had no idea how much time was elapsing.
Factual error: Petra is reading some details about the size of a murder weapon used to commit 6 similar murders. The diameter of the weapon is estimated at 77 centimeters. It says according to Petra's ruler, 77 centimeters is 3 inches. This should be 77 millimeters as 77 centimeters is about 30 inches.
Continuity mistake: On Page 69 (Part One: Blood Sport) the Owner of the Kelly Fruit Company is called Hubert, but on page 217 (Part Three: Wreckage), his name changes to Henry.
Continuity mistake: In Part 3, Chapter 33, two news reporters come to see Annie and interview her about the missing policeman. She walks out with a shotgun full of "double-ought buck", fires a warning shot, and then when she re-enters the house she magically has a rifle, not a shotgun.