But it is not a masterpiece. The philosophy is fine (if strident), the political theory is very well thought out and well stated.
That alone does not make a masterpiece. You may value a book for the thoughts in it, but object quite validly to the way in which the book is written. It's just not a good novel, qua novel. The characters are simply lay figures that are posed in positions by the artist, the dialogue is awful (people don't talk like that and never have), and the plot has holes you could drive a two-ton truck through.
Compare any of Rand's dialogue to, say, a conversation between two of Kipling's characters in one of his English short stories, or two of Mark Twain's characters in Huck Finn. No comparison.
You’re talking style and I’m talking content.
When it comes to style, there are many novels (some worthless) that stylists would consider as “masterpiece” works.
When it comes to content, Atlas Shrugged is a masterpiece novel that’s right up there with Les Miserables.