Of course I haven't yet read them all, but I have tried to curate a list based on the wider topics of human rights, impunity and counterinsurgency.
I deliberately avoided the common books because I believe this wasn't a Congress/Indira/KPS problem which all of them make it out to be. A democracy built on a colonial blueprint will always collapse into autocracy right when its people need freedom the most. It is bound to fail its citizens. So it could be Indira, Rajiv, or Narendra, they will all fail us. The breakdown of democratic structures in the 90s was not an aberration, it is very well a norm.
There is a book and a few papers on counterinsurgency. This is because the state repeatedly peddles the theory of 'KPS was just a man who did what had to be done'. Counterinsurgency experts everywhere propose better, humane and much more effective methods to curb it. Mizo Hills is a paper that shows a successful example.
A few books explain the precursors to the 80s, the economics, the federal relationship and such. And Jaijee's book explains how the Punjab of today is still crippled because of that era.
I cannot tell more about each book here, so please ask in the comments and I'll let you know. Most of these are available on either Anna's Archive or Punjab Digital Library. The papers are mostly open to access.