1. There are a LOT of movie adaptations of books.
2. Many of them are fine and ok movies, but terrible adaptations of the book.
3. Many of them are carbon copies of the book in a film version, but are not very good movies.
But there is one glorious exception: Breakfast at Tiffany's. Ok, technically not a book but a novella, and yet still the best I think there is. Close second award goes to the Lord of the Rings trilogy, but we will see them later on in the series.
The novella by Truman Capote is first of all, brilliant in its own right. Everyone should read it. But what the movie does that is so spectacular is that it adapts the novel, so that the movie has a distinctively different moral feeling, and yet at the same time, it is so true to character, description and dialogue, it feels like watching the same characters doing exactly the same things as in the novella, with an entirely different outcome, and it is ok. It makes perfect sense the way the movie plays out. The noted differences are important and anything but arbitrary. The movie is just Classical Hollywood glammed up a bit and it's delightful to watch.
And on an entirely different note, it is one of my favorite movie posters of all time.