By "main" civilization I mean the ones that are taught at school.

I'm reading a book on history, I don't know much history because at school the class never caught my attention, but now that I've graduated I really want to learn about our past.

The book I'm reading says the following in a chapter about Mesopotamia:

- The first civilization, Sumeria, developed in around 4000 BCE (I'm aware they often round dates a lot, this book is intended for teenagers)

- Akkadia was led by King Sargon I around 2300 BC. The Sumerian city-states Sargon I united fell to Babylonia around 1900 BCE

- Babylon was led by Hammurabi to create the Babylonian Empire around 1800 BCE. His empire was conquered and destroyed around 1500 BCE.

- The kingdom of Assyria rose around 1400 BCE, and the Assyrians were defeated by the Medes, Persians and Scythians in 612 BCE.

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Here's the problem: at the end of the chapter, they give me a mnemonic device to remember the order of the mesopotamian civilizations in order, which is the following:

- Sumerians > Assyrians > Akkadians > Babylonians.

So now I'm either mixing up the terms civilization, kingdom and empire or the book has a problem. With the information I first gave, wouldn't the order be:

- Sumerians > Akkadians > Babylonians > Assyrians

Because how can the Assyrians predate Babylonians in the book order if the Assyrian kingdom rose around 1400 BCE, while the Babylonian Empire was already there 400 years before, in 1800 BCE?

I'd appreciate it if someone could give me some answers. I know the book is incomplete in terms of information, you can't possibly fit all of history in one 400-page book. I'm reading this one aimed at teenagers so I can get the big picture, so that then I can move on to more detailed and complicated information on specific moments of history.