I'm looking for a realistic apocalyptic book

For context, I just watched Threads (1984), a british movie about how the cold war scalates in nuclear warfare. The film depicts the consequences of this event in a very harsh way, and jumps years ahead showing how society decays. (I definitely recommend it)

Now, because I'm somewhat masochist I'm looking for a book showing a similar scenario (plus if they're grounded in reality) the couple of books I have read about apocalyptic events always show some hope at the end, but I don't like that. I'm not interested in post apocalyptic novels, I'm interested in a story that explains how the apocalypse comes .

Oh,and I already have read The Stand by Stephen King (I mention that because it seems is the apocalyptic book for default haha) Thanks in advance!