The book follows a young man named Jacob who, after stumbling upon the murdered body of his grandfather, has the desire to find the children's home his grandfather once resided at. He is able to talk his father into taking him by appealing to his father's senses, and they head off to an island near Wales. Once on the island Jacob wants to see if he can find the house but his father has reservations. Jacob ends up losing the kids his father sends him with, they don't want to hang with him anyway, and he stumbles upon the house, the secret it holds, and the residents still there.
Up to this point the movie and the book are relitively similar, with a few minor differences. It is the end of the movie that has been changed, and I did not like it.
I am not neccesarily a book purist, meaning I don't always think a movie needs to follow a book line by line. The TWILIGHT books and movies did that and I found them both incredibly boring, especially the movies. I had other issues with the books. However, the movie should only change things if it adds to the story, not just for time, space, or character dimensions. The characters remained basically the same but the changes to the ending didn't work as well as the way the book ended.
The acting was okay, some of the characters weren't as developed as they were in the book, which seemed a little silly, and the relationship between Jacob and his grandfather wasn't as strong in the movie as it felt in the book. I honestly think that is typical though when a movie is made from a book. Often times I feel that the book lets you feel more than the movie usually does.
The movie wasn't too bad though, so if you have a chance to see it, go for it, it isn't bad and you can watch most of it with your younger children (there are some issues with a little bit of violence but nothing gory).