As a homeschooling parent, I assigned my 16 year old daughter to read the original Ray Bradbury novel, and then we purchased this movie and viewed it. She then wrote a report on the differences between the book and the film. The differences are what most of the reviews have been about, and there are many differences, for sure. However, there are some significant similarities, also. Without getting into details and giving away the ending, you will be better off if you realize that this is a modern re-telling of the story. From that perspective, it is a good movie. I gave this a 5-star rating in part to compensate for some unfair reviews that are based on the differences between the movie and the book.
The main concept from the book that carries over into the movie is the importance of books to society (which represent knowledge) and the importance of preserving that knowledge for the betterment of humanity.
I will warn any parents that this HBO film is not rated. I suspect that it would be given either a PG-13 rating or R (I would lean towards R). There is a lot of violence, but it is not gratuitous (most is people being pulled out of hiding and beaten, but the camera views it from a distance). There is strong language, too, whereas the F-word is used maybe a half a dozen times. To be fair, though, there is strong language in the book, but not that specific word. The writers didn't go overboard with the profanity, though (not like "Die Hard" which comes to mind).
All in all, it is a fresh look at an old book, that was filmed well.