As with any movie, the book is always better. What was an hour and a half movie seemed more like half an hour. I did love the movie, just not as much as the book. The actors portraying the characters were pretty close to the descriptions in the book, and the movie followed the book more or less. There were many book parts left out of the movie, but the important details were there.
I've seen this story compared to Twilight. Fallen is the same genre as Twilight, the young adult/romance genre. I've also seen reviews that criticize the religious connotations of Fallen. It's a story, and that's all. Angels and Lucifer provide a backdrop for this story, but it's just a YA romance, like Twilight and vampires and werewolves.
Overall, there was a good story line. The movie felt rushed. The characters, while portrayed well,were under developed. Some of the scenes/visual effects were a little hokey, and that's to be expected when presenting the supernatural. But the movie flowed smooth and quick, it certainly did not drag (as some parts of Twilight did drag). If you read the books, you could pick apart all of the missing lines and scenes. I did read the books, and watched the movie for pure entertainment value. If you read the books and liked them, then give it a try. If you didn't read the books, and you don't like young adult romance with a supernatural flare, this will likely not be your type of movie.