I'm still undecided about this one. Is Hanna Baker a realistic portrait of a suicidal teenager? Are her actions coherent with the character she is impersonating? 
 Many questioned Hanna's motives as not enough "serious" to trigger suicide thoughts but teenagers are oversensitive and, as the author pointed out, many "minor" episodes could lead to a snowball effects, especially if combined with one or two dramatic events as in Hanna's case. 
 Therefore I think the author did a good job in portraying the slow unravelling of a fragile fifteen years old, her increasing feeling of loneliness and neglect and even her egocentrism. 
 What left me puzzled is the means chosen by Hanna for her "suicide note" which make me think more of an artificial device to make the book more appealing than anything else. 
 What is the purpose of this complex sham? Why would a girl in 2011 choose to record her suicide letter on a cassette tape? Is it possible that her none of her intended recipient had never seen a cassette tape in their entire life, let alone the means to reproduce them (Hanna herself had to borrow the tape recorder). 
 Her tone, in the recordings, is mainly a vengeful one - understandable but I'm not sure about its realism - but if she wanted to make people feel guilty she could simply have sent each of them a letter exposing their "crimes". Instead she creates this chain of culprits forcing each of them to listen to her entire story and then forward it to the next in the list, threatening them with a backup set of tapes that would be publicly released if any of them interrupted the chain but what is the purpose? If she wanted to shame her recipients, why reveal their crime only to the other twelve accomplices? Why not reveal her story to the whole school to begin with? 
 To me it feels ad if the author was just trying to find the most appealing and original literary escamotage, one that could create more suspense and emotion than a long suicidal letter. 
 Besides, his tone is so didactic that his purpose is evident all along. His writing style is forced and not realistic at all: Hanna's and Clay's often sound like they are reciting a leaflet about bullism of suicide. 
 Moreover, Hanna includes in her list people who are not responsible of her suicide and it is really difficult to understand why she would submit them to such a torture. On the other hand, the most despicable of her bullies is not in the list: she may have thought that, given his crime, he would have interrupted the chain in order to avoid exposure but, again, she had a backup set of tapes for this! 
 A partial explanation could be that she wanted the people who wronged her to try and redeem themselves by denouncing this particular bully but, along her tale, Hanna never seem interesting in correct some injustince, expecially if it was not directly related to herself. 
 As you can see, it is diffucult to like Hanna, a trait of the book that I actually appreciated as one of the most realistic; Asher is not trying to make you condemn bullism because the victim is pitiful but because it is wrong in itself. On the other hand he doesn't want to totally alienate the reader so he chooses Clay as narrator: a good, sympathetic kid full of loving thoughts toward Hanna. unfortunately, despite the good intentions Asher falls victim of the same prejudices he's trying to stigmatize: Clay often expresses sympathy or love towards Hanna because he is sure that her bad reputation is undeserved. The bad reputation being that Hanna was not the slut everyone thought her to be. But that's exactly the point: what if Hanna had really made out with more than one guy? Would have she deserved to be treated like a slut? When will we ever stop to call a girl slut if she has more than one sexual partner? 
 In the end this book has many good intentions but I'm afraid that most readers (and viewers of the show) actually liked it because of its gossipy side - let's see who did what and which dirty secrets these teenagers hide - that for its social intent.