First Season : pretty good.
The story was build up smoothly, adding more suspense as the mystery was being unfolded, with a solid soundtrack, nice performances and the air of gossip girl.
Second Season : Okay
Not bad, but not as good as the first one. Nice addition of new characters and smooth character development.
Third Season : Try hard
Boring and like a bad version of the first season. Tried hard to shock and make things scandalous and edgy, but did not succeed.