I'll try, although I don't think I'm qualified enough.
First of all, what he's talking about is usually described as different stages of _civilisations_ in english literature. However, he goes into much length to explain why he talks about ethnoses instead: in sub sense, it's a different definition, and a group which is smaller than what you usually call a "civilisation", so this distinction is important. It's derived from the word "ethnic", but again, he's very particular that it's not exactly the same as ethnical group in a genetical sense, although one usually correlates to another.
In general, it's very hard to summarise his work, because he goes into a lot of details that are really important to understand his ideas correctly. Unfortunately, it's very easy to misunderstand them, and sometimes in some very awful ways, if you just assume that the words he uses have meanings that you usually ascribe to them.
Then, he describes different stages of lifecycle of ethnos. Once again, there are stages that you would expect, from birth to death, but he adds a lot of detail, describing how an ethnos can be both in a dynamic arc going from beginning to an end, but also in a static, balanced state that can continue, without outside interference, for an eternity. He's a historian with a deep knowledge of very wide array of different human eras and places, and draws a lot of examples to make his point from all over the human history.
After that, he tries to describe the underlying forces that influence this process. He goes through all possible theories and finally arrives at his concept of "passionarnost" (derived from passion) to describe the cultural energy that drives these transformations.
After reading other contemporary books on the matter, such as Guns, Germs and Steel, and Neil Ferguson's Civilization, as well as dozens of articles and blog posts discussing these things, I think that his analysis and thoughts are one of the most interesting and engaging ideas about it.
First of all, what he's talking about is usually described as different stages of _civilisations_ in english literature. However, he goes into much length to explain why he talks about ethnoses instead: in sub sense, it's a different definition, and a group which is smaller than what you usually call a "civilisation", so this distinction is important. It's derived from the word "ethnic", but again, he's very particular that it's not exactly the same as ethnical group in a genetical sense, although one usually correlates to another.
In general, it's very hard to summarise his work, because he goes into a lot of details that are really important to understand his ideas correctly. Unfortunately, it's very easy to misunderstand them, and sometimes in some very awful ways, if you just assume that the words he uses have meanings that you usually ascribe to them.
Then, he describes different stages of lifecycle of ethnos. Once again, there are stages that you would expect, from birth to death, but he adds a lot of detail, describing how an ethnos can be both in a dynamic arc going from beginning to an end, but also in a static, balanced state that can continue, without outside interference, for an eternity. He's a historian with a deep knowledge of very wide array of different human eras and places, and draws a lot of examples to make his point from all over the human history.
After that, he tries to describe the underlying forces that influence this process. He goes through all possible theories and finally arrives at his concept of "passionarnost" (derived from passion) to describe the cultural energy that drives these transformations.
After reading other contemporary books on the matter, such as Guns, Germs and Steel, and Neil Ferguson's Civilization, as well as dozens of articles and blog posts discussing these things, I think that his analysis and thoughts are one of the most interesting and engaging ideas about it.