Marcus Aurelius wrote these notebooks for himself, on campaign, with no intention of publishing them. That is most of why they last. There is no audience being played to and no argument being won - just a man returning, again and again, to the same handful of difficulties.
He keeps circling one idea: that a great deal of what troubles us is our judgement about a thing rather than the thing itself. Read a page at a time rather than straight through. It was written in fragments and it reads best that way.
Free, carefully produced edition from Standard Ebooks, translated by George Long.