I don't know whether it's better or worse that you are a fan of the original Tintin comics before seeing Steven Spielberg's adaptation. On the one hand you will have better knowledge of the ins and outs of the characters, the slapstick, the generally jovial and adventurous tone etc. On the other hand you will probably, as with any adaptation, be constantly aware that it's not exactly the comic Tintin you know and love.
The story follows Tintin (Jamie Bell), an investigative reporter and adventurer who one day happens across a mysterious model ship. He soon learns it is sought after by the villainous Sakharine (Daniel Craig) as it is the key to uncovering the "Secret of the Unicorn."
When The Adventures of Tintin works it really works, providing some truly fun and exciting action set pieces that fits comfortably in with the best of this past summer's best blockbusters. Bringing the action and overall story to life is the wonderfully done, visually arresting motion capture animation brought to worldwide prominence with Gollum in Lord of the Rings and later giving us the likes of King Kong (directed by Tintin's producer, Peter Jackson) and Avatar. The technology has been criticised in the past, often to do with the "dead eye effect" (notably in the likes of The Polar Express and Beowulf), but Spielberg puts the technology to the best use possible here, providing a rich and vivid world, the motion-capture allowing them to do things that might not have had the same effect (or might not even have been possible) in regular 2D.
The film's main problems lie in the way in which the overall mystery-adventure plot is told. Perfectly serviceable for film though the mystery may be, the execution of it at times feels languid and stodgy, like it's stumbling along from one eye-catching setpiece to the next. Also, the way in which some of the on-going mysteries are solved seem rather convenient in order to move things along. For instance, Tintin will be struggling to think of what do next and with a "lightbulb above the head" sort of moment will figure it out and off we go to the next mystery. Maybe that sort of thing is in the original comics (I'm not overly familiar with them) but it didn't entirely work in this particular adaptation. It's just lucky all of those big set pieces are as entertaining as they are or the movie would be in real trouble.