Revealing mistake: In the closing scene, you can see the modern curb & sidewalk have been covered with dirt.
Continuity mistake: When Books falls in the bathtub, Mrs. Rodgers goes in to help him, and about three seconds later, he emerges from the bathroom fully clothed in his robe and a towel around his neck.
Continuity mistake: In the bar room fight, Books fires three times, then once with revolver in his right hand. Gilliam picks up that same gun and fires three more times - a total of seven rounds from a six-shooter.
Continuity mistake: In the scene where Books and Gillam share a bottle of whiskey, as the camera changes angles the bottle label is always away from the camera.
Continuity mistake: When Books is in the barber shop talking to Mr. Beckham the undertaker, in different scenes Books' tie is either inside or outside his vest.
Factual error: As John and Mrs. Rogers are out for a buggy ride, Mike Sweeney comes up on them in his horseless carriage. You can see the Horseless Carriage plate on the rear of his car. These plates were not issued back when the film was depicted. (00:42:00)