Yes, it's one guy ranting about his life, and his dreadful relationships with his wife, his daughter, his son, and his other son, and his work colleagues, and yes nothing happens (except that it does), but what is astonishing is the way in which he is able to maintain the interest, varying the ranting, contradicting himself, illuminating the terrors of family life afresh on every page.
What happens? If you were skimming it, you'd miss it, and I think some of the reviewers here did just that. Just two paragraphs very close to the end, the content of the first shockingly, unbearably sad, the content of the second making the first explode with a grim tragedy (I missed this before I reread it a few hours later).
I read Catch 22 years ago, and enjoyed it, but it was nowhere near as technically skilled as this.
But not one to read if you're feeling a bit low.