Content warning Minor spoilers
I haven't read widely on the reaction and existing views on this book. At this point is is on that clearly has a passionate cult following, and has had a significant impact. I think both of these things are deserving.
It's a warm and very humane story of a sympathetic teenager's first year in high school. A series of letters written to the reader, Charlie, the point of view character, is clearly neurodivergent, and provides an 'outsiders' view of that transition period toward adulthood.
Due to sometimes long periods of time between the 'letters', the story cuts out the day-to-day life and skips straight from drama to drama, touching on all of the various complexities of teenager-hood, including sex, sexuality, drug use, anxiety, and both positive and abusive relationships. While it sometimes feels a bit like a checklist of controversial or complex topics, and Charlie's naiveté is a little tedious at times, these issues are dealt with in a mature, nuanced and think very humane way. Though there is a clear morality in play, it is not a preaching kind. To be honest, I can imagine the book being very eye-opening for teen readers, and importantly useful in its discussions and representations of sex, sexism, consent, drug use, sexuality, and more.
It writing style - explicitly wide-eyed and innocent - is occasionally excruciating, which is probably necessary, but was sometimes a bit of a grind for me, which is why I haven't gone all in on the five stars. In a minor point late on there is also a rather positive (though also ambiguous ) view of Ayn Rand, who I find to be so ignorant as to be basically evil, and which unsettles things. There's also what felt to me as rather than unnecessary abuse-and-repression angle, which I is a bit problematic because of how little it adds to the story overall.
I was also lucky to read this in an interesting manner. A friend organised an mailing list which meant that the 'letters' arrived in my inbox as messages. (On the dates written, which is probably a quirk - perhaps they should arrive the day after?) It gave the whole reading experience and extra twist, though did also sometimes have me losing track of what had come before.