Can some one please suggest some reasonably easy-to-read authors who have written reasonably historically accurate novels depicting what it was probably like to live in a civilization in its very latter stages of decline and its aftermath. An example might be Western Europe as the "Dark Ages" began to emerge at the end of the Roman Empire around 300-800 A.D. or so. Other examples might include the demise of the Egyptians, Aztecs or Incas, etc.

I want to develop a sense of what happens after the decline of real-world civilizations. What part of human nature causes it and why? How do people deal with it? I am not, for example, interested in stories that involve "magic spells" or anything that is purely fantasy. I'm looking for plausibility.

Obviously, this not related to rubber in any way... I'm just looking for some interesting reading.

What authors do you suggest and why???

Thanks