I read it in Russian after watching the movie, which I fell in love with. And to say "it's a good book"-say nothing. The way J.R.R. Tolkien succeed to depict all the characters, all places, battles, creatures- this whole world- is beyond my imagination. He even wrote the history of the Middle Earth with all dates. This book is a masterpiece.
Of course there are lots of moments that weren't shown in the movie and this is one more reason to read it. May be the only negative fact is that J.R.R. Tolkien goes deep into the long descriptions when you are anticipating for the action