I read the book by Jay years before the show was made, and it had always been a book that I still thought of from time to time, because the story and concept were so interesting. I think the first season did justice to the book in the way that it can haunt you for a long time. I loved the first season, though it definitely had some scenes that were very hard to watch, which was the point.

It made sense that they would make a season 2 given its success (purely for the money only though, probably). It was okay, it gave more look into the lives of those left behind (which the book didn't have) but it truly should have ended with the second season. I dind't even bother watching the third because it had moved away way too much from the original intentions of the first season.

I definitely recommend watching the first season! Watch the other 2 at your own leisure, but I don't necessarily recommend it.