Questions of good/correct vs bad/incorrect are largely a matter of culture, point of view, lineage, relationship to words like "authentic", relationship to the concept of "oldest", and the like.
There is a ton of helpful information in that monster of a book.
Even if some of it is not to your liking, doesn't fit with your cultural, traditional, or intellectual aesthetics, or whatever, still, by reading it, you will understand aspects of some of the core debates within the Theravada and many debates outside of the Theravada and even those between the various Theravada strains and the rest of the spiritual world that those who haven't never will, and, in this, you will distinguish yourself and be able to raise the level of discoure on that book and its concepts, which is generally abysmal.
Teachers, such as many often discussed on this forum, routinely demonstrate by their characterization of the messages of the Visuddhimagga that, if they did read it once, it was so long ago that they no longer remember what it actually said.
If you find that you are able to actually read the whole thing carefully and finish it, you will have demonstrated a level of discipline rarely found today, a level of discipline that is the kind often needed to get to the level where you experience what that book is talking about.
If you read that book and also learn to practice well, then you will doubly benefit.
Good luck!
