I saw the film a while back and really enjoyed it. I bought the book for my daughter Celyn's 9th birthday and read it to her (she's registered blind and couldn't watch the movie). We finished it last week in hospital. She did fall asleep a couple of times but to be fair she was recoving from a general anaesthetic. 
 The book is very different to the film. Both share some comical Vikings and a weedy 'hero' named Hiccup. Both contain dragons. That's about the end of the similarities. In the film the young Vikings are trained (in a mixed class) to battle dragons. In the book the young Vikings (boys only) own and train dragons. 
 Actually I lie. Hiccup is very similar in character. An outsider at odds with his societal norms. A thinker in a world that's all about fighting. Also as in the film there is a hostile uber-dragon (two in fact) that is truly gargantuan. 
 The book is good fun but a touch too silly for there to be any real emotional connection with the characters - always a minus for me. It has some clever bits, some funny bits, and Celyn and me certainly didn't waste our time reading it. A solid 3* for fun. I would rate the film more highly, and that's a rarity for me. 
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