[Warning: This article contains spoilers about all 13 episodes of Netflix's 13 Reasons Why, as well as the book. Read at your own risk!]

13 Reasons Why, Netflix's adaptation of Jay Asher's YA novel of the same name, hit the streaming service on Friday, and if you haven't already binged the whole thing... what are you waiting for?!

At a winter press day earlier this year, Asher described Netflix's version as a "perfect" adaptation of his book, but while that may be true in terms of quality, it's not technically accurate. In fact, there are a number of key ways that the TV version of 13 Reasons Why makes significant departures from its source material.

For the most part, these differences enhance the TV show, taking the world Asher created and expanding on it in ways that are interesting and often heartbreaking. (And understandable - after all, 13 hours of programming is a lot more real estate to work with than 300 pages.)

Here are 13 key ways 13 Reasons Why broke from the book, and why each choice was an important one.

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1. It doesn't take place in a single night

The most significant difference between 13 Reasons Why the show and 13 Reasons Why the book is that the book takes place in a single night, with Clay wandering around town listening to the tapes, with Hannah narrating events that took place in the past. The show, on the other hand, covers several weeks. The effect of this change can not be overstated. Most importantly, we get to see the long(ish)-term effects of Hannah's (Katherine Langford) suicide on her classmates and parents, as well as how Clay's (Dylan Minnette) perception of his peers changes as he progresses through the tapes. The expanded present-day timeline also includes important events that are nonexistent in the book, including Jessica (Alisha Boe) going down a path of self-destruction after realizing the truth about her assault, Hannah's parents (Kate Walsh and Brian D'Arcy James) finding out about the tapes, Tyler (Devin Druid) purchasing a gun to put an end to the bullying he deals with every day, and Sheri (Ajiona Alexus) finally taking responsibility for knocking down the stop sign (as well as a number of additional changes that are discussed below).

2. Hannah's parents sue the school

One key aspect to the aftermath of Hannah's suicide is that her parents file a lawsuit against the school for failing to prevent their daughter's death. Making things extra awkward? The lawyer representing the school in the case is none other than Clay's mother, Mrs. Jensen (Amy Hargreaves). The lawsuit plot prompts a number of interesting discussions among the adults in the show about what steps the school could have and should have taken to prevent its students from being bullied - and whether there were overt warning signs that administrators might have missed. It also proves for an interesting mystery/twist about what Mr. Porter (Derek Luke) will do with the tapes once he gets them, since Tape 13 implies that he not only missed an opportunity to save Hannah's life, but also told her to essentially move on from a sexual assault.

3. Alex gets shot

It's unclear at this point whether there will be a Season 2 of 13 Reasons Why, but the ending of Episode 13 certainly seems to indicate that that's the intension. There are a number of cliffhangers at the end of the show, including the revelation that Alex Standel (Miles Heizer) is the latest Liberty High student to attempt suicide. Or did he? We never actually see Alex shoot himself, and it's the principal who says Alex shot himself, but the EMT merely says that the patient is a "17-year-old male with a gunshot wound to the head." Is it possible that Tyler shot Alex? Regardless, the show ends with Alex in critical condition after taking a bullet to the head.

4. Courtney is gay

In the book, Hannah and Courtney pretend to have a sapphic sleepover so that Hannah can expose whoever's been taking pictures outside her bedroom window. The photos Tyler takes of Courtney and Hannah giving each other backrubs and of Courtney acting like she discovered vibrators in Hannah's underwear drawer are for his own personal enjoyment; the photo of Courtney and Hannah that she discusses in the book is an awkward yearbook photo of them standing together at a party, after Courtney uses Hannah for a ride to said party and then spreads a rumor about her there. In the TV show, Hannah invites Courtney (Michele Selene Ang) over for a study date, they start drinking, and Courtney - who clearly has romantic feelings towards Hannah - starts kissing her. The photo that causes a stir is one that Tyler snaps of them kissing on Hannah's bed and distributes to the whole school. The fact that Courtney doesn't want anyone to figure out that it's her and Hannah in the photo because she doesn't want anyone to know she's gay adds a new topical layer to the storyline in the show. And, she's not the only character whose sexuality is retconned in the series - Tony (Christian Navarro) is gay in the series as well.

5. The other characters are more sympathetic

In the book, we only get Hannah and Clay's (usually unfavorable) takes on their classmates. But thanks to the show's timeline expansion, the fringe characters become more fully developed and we get to see aspects of the other students' home lives that makes some of them more sympathetic. It's important to note that the show doesn't try to excuse any of the teens' behavior, but knowing their back stories adds a layer of explanation to some of the plot points beyond just "that person's a jerk." For instance, in the show, we learn that Justin Foley (Brandon Flynn) comes from a horrible home that includes a drug addict mother and a revolving door of abusive stepfathers. Alex's father (Mark Pellegrino) is a cop who encourages him to fight to prove his manhood. And Courtney doesn't want to reveal that she's gay because she's seen the discrimination her gay fathers have faced and doesn't want their family to face any negative repercussions from her coming out.

6. Hannah gets some things wrong

In the show, Clay and Tony have an exchange in which Clay argues that Hannah's not telling the truth and Tony responds that she's telling "her truth." Reading the book, we more or less have to take Hannah's words at face value. But in the filmed version, we see that she did get a few things wrong - things that could potentially have stopped her from making her fateful decision, including the fact that Zach Dempsey (Ross Butler) keeps the letter Hannah writes him about how depressed she is, rather than discarding it. Also, Jessica claims that it was Hannah who stopped coming to Monet's, not her and Alex. In other words, we get to hear other characters' "truths" in addition to Hannah's.

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7. Clay's classmates try to stop him from passing on the tapes

Another effect of expanding the story to encompass several weeks rather than a single night is that we get to see Clay's classmates react to what they know he's learning about them from listening to the tapes. Unfortunately, this leads to a sometimes misguided subplot involving several of Clay's classmates banding together to form a gang of sorts, in order to prevent him from passing on the tapes. The High School Mob storyline is, for the most part, a melodramatic mess that distracts from the more emotionally grounded central narrative.

8. The person killed in the crash is Clay's good friend Jeff

The Butterfly Effect aspect to 13 Reasons Why is that the events Hannah discusses on the tapes create a chain reaction that leads to the accidental death of one of their classmates in a car accident. In the book, the student killed is a random person whom Clay describes as "just one of the many faces at school I never got to know." But in the show, the victim is Clay's good friend Jeff (Brandon Larracuente), whom he tutors and who helps bring Clay out of his shell, convincing him to go to school dances and talk to Hannah at a party. Because Clay was so close to the victim, he snaps at Hannah when she tries to console him at school and accuses her of trying to make the death all about her - sending Hannah into the final downward spiral that culminates in her suicide.

9. Tony follows Clay the whole time

In the book, Tony tracks Clay down at a diner and stays with him while he listens to his own tape. But in the show, Tony plays a much larger role and essentially stalks Clay for weeks and months (to the somewhat comical frustration of Tony's boyfriend), acting as both a shoulder for him to cry on and as a bodyguard to protect Clay from the Tape Mob. He also acts as a source of comfort for Mr. and Mrs. Baker, and we learn that Tony rushed over to Hannah's house on the day of her suicide after he received the two sets of tapes, but got there too late.

10. Hannah is explicitly raped by Bryce

There are several instances in which 13 Reasons Why the series explicitly shows what's only implied in the book. Hannah being raped by Bryce (Justin Prentice) is perhaps the most significant of those. In the book, Hannah describes Bryce putting his hand inside her bathing suit and says simply that he "didn't stop there." She also notes that she never told Bryce "no" or pushed his hand away, although he could clearly see that she was crying. In the show, Hannah fights back until Bryce physically overpowers her in the hot tub. There's no room for debate about whether or not this was an assault.

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11. Clay isn't a saint

Let's be clear: We love Clay. He seems like a great guy, and is certainly the most dateable member of the Liberty High junior class (at least among the people we see). But he's not perfect. The Clay depicted in the show is a more flawed character than in the books. Even though his intentions are rarely malicious, he gives in to his worst impulses on a number of occasions, including masturbating to the picture of Hannah and Courtney that's making the rounds, and getting revenge on Tyler by playing voyeur himself and texting a picture of Tyler's naked butt to the entire class. And in some ways, he's no better than the gossip mongers who make Hannah's life a living hell, especially when jealousy prompts him to be rude to Hannah after he hears the rumors about her and Justin Foley.

12. Clay records Bryce's confession

Another dangling thread at the end of Season 1(?) is that Clay secretly records Bryce confessing to raping Hannah. Additionally, the order of tapes is switched in the show: Clay's is now 11, not 9, meaning he's supposed to pass the tapes on to Bryce. But instead, he goes to Bryce's house hoping Bryce will incriminate himself (which he does, and beats the crap out of Clay in the process), and skips over Bryce in the chain, passing the tapes directly on to Mr. Porter.

13. Hannah slits her wrists instead of taking pills

In the book, we're told that Hannah commits suicide by swallowing a handful of pills. However, in the show, Hannah's suicide is depicted in an extremely graphic scene showing her cutting her wrists in a bathtub - and screaming in pain as she does so. It's a cringe-worthy, sickening few seconds, and it's a safe bet that more than a few viewers will find themselves turning away from their screens. Again, 13 Reasons Why is unflinching in its portrayal of other events in the lives of Hannah and her classmates, and her death is no exception. The show's aim is to examine the horrific nature of suicide and its aftermath, and showing Hannah peacefully going to sleep after taking some pills would not accomplish this (and may have even led to some accusations that the show is romanticizing suicide). The gruesome bathtub scene hammers home the point that this was Hannah's decision, and wasn't an easy one in a number of ways. It's incredibly difficult to watch, and you want to reach through the screen and knock the razor blade out of her hands. No doubt that was the intention.

All 13 episodes of 13 Reasons Why are available to stream on Netflix.