If you've ever read the book by David Brin, you will realize that Costner made a decent film from a terrible story.
I've read a whole lot of bad reviews for The Postman. I had rented the movie back in 98, more out of curiosity and not seeing anything else on the shelf that looked interesting. Yes, Blockbuster Video was still around then.
The movie surprised me. It wasn't terrible, just overly melodramatic in parts. There is solid acting, decent character development and the sets really gave a post-apocalyptic feel.
Since I thought the movie was decent, I purchased the book and figured it was probably better.
Boy was I wrong.
Brin's book of the same name reads like a feminist treatise. It's truly some of the most woke garbage I've ever read. The main character is some pseudo-intellectual vagabond who befriends people along his travels and those people actually change the world, not him. He's basically an afterthought and a simp! Costner's version of the character is far more empathetic. He's a flawed man who comes to grips that he has to personally act to make the world change, not simply hope it will change. The fact that Costner was able to take Brin's rubbish and turn it into a watchable movie, is credit to his talent as a director.
The Postman is not a perfect movie but it's thoughtful and entertaining, something that the book The Postman was not.
Give it a viewing.