Meg
You need to know this first: the movie has almost nothing to do with the books. They both have vikings, dragons, and a similarly unlikely hero named Hiccup. But they remain entirely separate entities.
That said, I liked them both. The movie was one of those rare 3D movies that was worth the extra cost. The animation was thrilling, we had a main character worth rooting for, and a lesson that kindness and cooperation are more effective than violence. All in all, a good flick.
But the movie doesn't touch the books. In fairness, much credit must be given to David Tennant's really excellent narration (note: the first book isn't narrated by David Tennant and, as such, isn't nearly as good). But, there's this whole, hilarious world in the books, brought so vividly to life by David Tennant and it's such a fun place to be. Laney and I are in the car about an hour and a half every day. And we listen to a LOT of books on tape. But nothing has come close to these in terms of genuine entertainment value for both child and adult.
If you have a long car trip ahead of you, trust me: these are the books to get you through it (except the first one... maybe read that one yourself).
And Camicazi is 10 times the girl hero that Astrid is. I love Camicazi so much.
Laney:
I like the books better. The books have more adventure because there's more of them. Also, Toothless can talk and is funny.
The books are much funnier than the movie. I like all the characters. I like Zigarastica and Stoik and Hiccup and Camicazi the most. Hiccup is the main character. He is a very small, ordinary looking boy. He is not like the other Hairy Hooligans because he actually thinks instead of just bashing things and yelling and screaming. He can speak Dragonese which means he can talk to dragons. He's also nice to the dragons instead of just screaming at them.
My favorite of the books is How to Cheat a Dragon's Curse because it really shows how Hiccup can stand up for his friend, Fish Legs. Hiccup is very loyal.
Toothless is Hiccup's dragon. He is disobedient, not all the time, but sometimes loyal. He's lazy. Once he did a poo poo in a helmet, but it was a bad guy's helmet. I think he loves Hiccup but he doesn't always show it. Toothless is really funny.
While the movie has almost nothing to do with the books, it does have the same name and Hiccup is also very skinny and small. I still enjoyed the movie, but compared to the books it's just the big pile of poo poo in the bad guy's helmet.