This article explains differences between the book Thirteen Reasons Why and the Netflix Original Series 13 Reasons Why. This article contains spoilers between both the book and the show. Read at your own risk.
"Cassette 1, Side A" vs "Tape 1, Side A"
- In the book, Justin Foley (Book) starts bragging about his date with Hannah Baker (Book), and people then spread rumors about Hannah, providing the reason she put on the tapes. This happens in the show, except rumors are spread based on a photo Justin Foley shows his friends. Bryce Walker takes Justin's phone and shares the photo.
- Clay listens to all of the tapes in one night. If you were at all frustrated by Clay's slow progression through Hannah's tapes in the TV show, you'll probably be a big fan of the way Asher originally chose to do it. After receiving the box of tapes on his doorstep in the book, Clay binges them in one sitting. In the show, Tony tells Clay that he's "the slowest yet" of all of the listeners.
- Clay doesn't figure out Tony is following him right away. Although Clay has a run-in with Tony in episode one that confirms he's the one Hannah made responsible for watching everyone on her list, book Clay doesn't realize that it's Tony until he listens to the fourth cassette tape (after stealing Tony's Walkman).
- Social media doesn't factor into Hannah's bullying. Sites like Facebook and Twitter certainly existed when Asher published the novel in 2007, but they had yet to become all-consuming forces in the lives of teenagers like they are now. There are references to Clay's cell phone, but the photos of Hannah that Justin and Tyler spread through the school via group text in the series are only word-of-mouth gossip in the book. Rumors by themselves are definitely damaging, but actually seeing the images of Hannah passed around so cruelly adds a new layer of pain to her bullying.
- Clay doesn't have hallucinations about Hannah. Some of the more shocking scenes in the show happen when Clay has visions of Hannah bleeding out in the middle of the gym and at the school dance, and it's mentioned in passing that he used to take duloxetine to treat an anxiety disorder (which is why he can only handle listening to one tape at a time). This never happens in the book.
- The high school students are tamer, so to speak. Parties full of underage drinkers happen in the book (as do the horrifying rape scenes), but the show doesn't hold back from showing other realities of being a teenager today: smoking pot, having sex, driving drunk, cursing, etc.
- Clay injures himself in another way. Distraught and distracted by the tapes, Clay slams his bike into a car in the first episode, cutting his head wide open. He's just as unlucky in Asher's novel, except he gets a nasty slice on his hand from a fence.
- Courtney Crimsen is still the worst, but in a different way. Book Courtney still has a reputation as the strait-laced nice girl at school, and she also sleeps over Hannah's house to help her set a risqué trap for the Peeping Tom who's been following her around. Instead of getting drunk and making out during a game of Truth or Dare, however, the two give each other a back massage in front of the guy watching them. Courtney, who isn't gay in the book, then spreads nasty rumors about Hannah being a slut in an attempt to raise her street cred at school.
- The order of the tapes is different. In the show, Clay is the 11th person to receive the tapes and chooses to skip number 12 (Bryce, a rapist who would probably destroy the tapes if he got them) and give them to the last person on the list instead, Mr. Porter. The resolution is less clear in the novel, since Clay is ninth on the list, and simply mails them off to number 10. There also aren't any scenes of his classmates conspiring to keep the tapes from being discovered.
- Clay never confronts Bryce or records his confession. Because the order of the tapes is different in the book and none of the kids are trying to stop Clay from listening to all of them, Clay doesn't try to bring Bryce to justice for his actions. He never records his confession of raping Hannah, or gives "side 14" to Mr. Porter.
- There isn't a lawsuit. The Bakers only appear in the book very briefly, and their lawsuit against the school doesn't exist. The only time they come up is when someone mentions that they've closed their shoe store (which is replaced by a pharmacy in the show) in the wake of their daughter's suicide.
- Clay's parents are barely in it. When Clay first starts listening to the tapes at the beginning of the book, his mom comes in to check on him and they have quick conversations throughout the night. In the show, his parents are in every episode (and what feels like every other scene), mostly because his mom is the lawyer tasked with defending the school district against the Bakers' lawsuit.
- Hannah's suicide is done differently.The scene of Hannah killing herself by slicing her wrists open with a razor blade is extremely graphic and difficult to watch. It's a huge departure from Asher's original portrayal of her death, which is referenced only when Clay says she "swallowed a handful of pills.
- Clay and Hannah aren't exactly friends. Some of the most touching, heartbreaking moments throughout the 13 Reasons Why show happen when Clay is mourning the future he and Hannah could have had or reliving memories from their close relationship. He pines after her for nearly the entire season, and is confused when she pushes him away after their heated makeout session at Jessica's party. The kiss still happens in the original story, but the lead up to it is different. They work at the movie theater together for one Summer, but Hannah says on the tapes that she wishes they could've been closer and gotten to know each other better. The two don't actually ever have a legitimate conversation until the night of the party when they hook up.
- The Monet's crew has a different motto. In an effort to update the book, Hannah, Alex, and Jessica's motto goes from "olly olly oxen free" to "FML."
- And Sheri has a different name. In the book, a nice cheerleader named Jenny Kurtz chats with Hannah during the Dollar Valentine fundraiser, and is later responsible for knocking over the stop sign that causes Jeff to die. Jenny is changed to Sheri on TV and pursues a relationship with Clay that she doesn't originally.
- Speaking of Jeff, he's a much more minor character in the book. It's hard not to crush on Jeff throughout the show. As a popular, well-meaning baseball player who takes pity on Clay's ineptitude with girls, he's instantly lovable, which makes his sudden death in a car crash because of Sheri knocking over the stop sign that much more painful. He still dies in the book, but since his character is a senior that none of the main characters are friends with, it doesn't have as big of an impact on Clay's life.
- Alex doesn't attempt suicide. Alex Standall openly struggles with fitting in at school and his remorse over what the group has done to Hannah in the show, and a scene of him dropping in Bryce's pool at one point suggests that he doesn't necessarily want to come up for air. It's revealed in the finale that he shoots himself in head, but not if he survives. None of this happens in the book.
- Tyler doesn't have a plan to shoot up the school. A disturbing scene in the show alludes to Tyler's plans for a school shooting (he opens a secret compartment in a trunk in his bedroom to reveal a stash of guns and explosives), but like Alex's fate, he doesn't do that in the novel.
- The book's ending is less complex.After listening to Hannah's tapes and wishing that he could've picked up on signs of what she was going to do earlier, book Clay reaches out to an old friend, Skye, who's been showing signs of depression. This also happens in the show, but since there's likely going to be a second season, more storylines are left open: Tyler's violent plans, Alex's attempted suicide, the Bakers' lawsuit, Sheri turning herself in, Bryce's rapes coming to light, and more.
- Clay's appearance is different. In the he book we can see how he is reacting on Hanna's stories and we can hear his thoughts but in the series, we can see his school life and what happens besides the cassettes. Clay is a much more important character to society on the series.