1. While Alden Ehrenreich (Tetro) was perfectly cast to play the charismatic—yet endearingly dorky at times—Southerner Ethan, he has higher aspirations in the movie version than in the book, from being just a sophomore basketball jock longing to meet an atypical girl to being a junior applying to every college to break free from Gatlin. This detail serves a purpose to fit with the film’s alternate ending, which will later be discussed.

2. The role of voodoo expert, librarian, and Ethan’s grandmother-like guardian, Amma—who’s played by the striking Viola Davis (The Help, Doubt), is really two characters in the book all rolled into one. Left out of the movie is Marian, Ethan’s mother’s best friend, librarian of the human world, and “Keeper” of all Caster secrets and books in the underground.

3. There’s little time to waste in this relatively short film, so Ethan mentions on a couple of occasions that his father is grieving from the death of his wife and is hiding in his study. But the father’s physical presence is completely omitted in the film; in the book, he is a constant dark reminder of Ethan’s upsetting home life.

4. Perhaps a little too cliché for the movie, Lena Duchannes—beautifully portrayed by the mature-beyond-her-years Alice Englert (Ginger & Rosa)—drives a retro pale yellow Mercedes Benz instead of the signature black hearse she steers in the book. However, she does not downplay the amount of dark clothes and black eyeliner that are characteristic of her Caster ways. All witches have to be at least a little Goth, right?

5. On-screen, Genevieve Duchannes, Lena’s ancestor from the Civil War, is so overcome with sadness from her mortal lover’s death that she brings him back to life with a forbidden spell, only to switch over to the dark side as a result. She snuffs her lover and then proceeds to make a fiery attack on all the soldiers in line—complete with deathly stares and lightning bolts. However, in the book, Ethan Carter Wate (Ethan’s ancestor), rises for a second from the spell, but falls dead again on his own, without Genevieve going Rambo on everyone. Both the film and novel, though, keep intact the tradeoff for using such a forbidden spell: Genevieve’s ancestors are forever cursed to be claimed to the light or dark sides when they turn 16, with no say whatsoever in the matter.

6. Besides sharing a common interest for historical flashbacks, Ethan and Lena go through the entire book “Kelting”—using the ability to have full-on telepathic conversations with each other, naturally saving themselves from texting overage costs. This magical aspect of the story is completely omitted from the movie.

Macon Ravenwood (Jeremy Irons)

7. Jeremy Irons (Die Hard: With a Vengeance, The Lion King) plays Macon Ravenwood, the local recluse who is nonetheless sharply dressed—and plays a larger role in pushing Ethan away from his niece, Lena, in the film. During their first meeting, after Ethan asks him if he can do any fortune telling, Macon takes hold of the boy ‘s subconscious and makes him robotically recite a grim future of marrying the high-school cheerleader, living a life of emptiness, and becoming the town alcoholic. This is a departure from the novel. What’s not mentioned in the film is that Macon is an Incubus—a dweller of the dark and one who has an insatiable appetite for mortals’ dreams. Although Macon is accurately portrayed showing up one night in Ethan’s bedroom, he’s actually there to steal bits of Ethan’s dreams, not to give the boy a stern warning to stay away from his niece.

8. Mrs. Lincoln, who is a bit of a Bible-thumper, is strongly depicted in the film instead as a fire-and-brimstone conservative. Brilliantly played by Emma Thompson (Sense and Sensibility, Love Actually), she has a standoff with Macon during a community meeting/witch trial of Lena at their local church and—SPOILER ALERT!—reveals herself as Lena’s vengeful mother, Sarafine, hiding inside of Mrs. Lincoln’s body, midway in the film—something that isn’t revealed until toward the end of the novel.

9. The Duchannes have it tough: they never know whether they’ll turn good or evil, but the curse doesn’t end there in the film version. Lena must also kill someone she loves in order to break the curse, a detail that isn’t part of the book.

10. The implications of Lena’s choice in becoming a light or dark Caster vary from the novel to the film. On-screen, going dark means Lena will become a starkly powerful evil witch. In the book, if she becomes dark, every light witch will die, and vice versa. Why would she care if the dark witches died? Well, as innocent as he may be, her beloved dream-sucking uncle would be a part of that lot.

11. Sometimes sacrifices must be made in the name of love. After a romantic snowy dance in the woods, Lena casts a spell and wipes out Ethan’s memory of her—à la Eternal Sunshine of the Spotless Mind—so he won’t have to bear living with a killing machine if she turns dark. No such thing happens in the book, and Ethan just has to roll with the punches of having a cursed girlfriend.

12. Shameless star Emmy Rossum’s sexy Siren character—Ridley Duchannes—is not only a shining example of what happens when a Caster goes dark, but also plays a major role in killing her cousin Lena’s one true love in the film. She seduces and mystifies Link, Ethan’s best friend, into accidentally shooting him with a real bullet instead of a blank during the town’s annual Civil War reenactment. This however, never happens in the novel—Ethan actually misses most of the reenactment—and instead, he falls to his death thanks to a stabbing by the evil Sarafine.

13. The Book of Moons shows up more in the novel than the movie. As far as curses go, if Casters use the forbidden “Binding Spell” in the witches’ handbook, they’re forced to do a trade—which, as example has shown, is never a good one. But, of course, history always seems to repeat itself, and Lena uses the same incantation Genevieve used to bring Ethan back to life. However, the horrible trade she faces is that her protective and caring uncle’s life is traded with the boy. In the film, Macon uses shape-shifter magic to trick everyone into believing he is Ethan during the Civil War reenactment, and is the one who gets shot by Link, then dies.

14. With his memory of Lena gone and now free of any ties to Gatlin, Ethan is as happy as can be in the final moments of the film, and stops by the library just before he goes on a college-visiting road trip to NYU. Running into Lena at the library jostles his memory, and the film ends with him screaming her name. In the book, the sequel is set up in an entirely different way, as the dark witches have disappeared but are still out there, and an omen about Lena’s 17th birthday surfaces.