What Is the Most Significant Book in Theology in the Last 50 Years?

I wish we could retroactively say that that had to die very early on. What is the most recent work of fiction you just couldn't put down? I started Christian Lavrenstater and have not worked my way all the way through it yet, but now it's in the US and I'm in Germany. And what is the most significant book in theology in the last 50 years? Maybe something by James Cone or Gustavo Gutierrez.