Book to Movie faux pas

Well as I get ready to watch the Last Air bender with my 9 year old son (which he has been counting down the days till it came out) I to start getting excited. Then the movie starts and they say Ang's name and for all of you who watch the cartoon on Nickelodeon and have seen the movie know what i mean. My son just says pretty loud that's not how you say his name. So after that and a few other Miss said A words i couldn't really enjoy the movie cause my son was fuming mad over what he feels is an unforgivable mix up. But it did get me thinking and wondering if the director ever saw the show or read the books? then i thought some more about other movies that i felt was like did they even read the book? So long story short I have decided to talk about it and see if I am the only one who feels that if you are going to make a movie based on a book or T.V show maybe you should actually watch or read it. Back to The Last Air Bender I did go back and watch it a second time with out my son and found if you got over the annoying miss pronounced words the movie is really good but unfortunately I don't think the other two books will be made due to the fact that it didn't do to well at the box office. Partly I think is because there are a lot of M.Night Shayamalan haters out there. I personally like his work and find that a lot of people just don't get him because it goes over there heads. I find myself explaining a lot of his movies to people. Also i feel that directors assume that everyone has read the books i feel that they did this with the Harry Potter movies. Especially the little things like the maunders map my husband was like how did that teacher (professor lupin) now how to use it. well since i read all the books i explained the whole thing to him and he pretty much said well that some important info that should have been in the movie I too have to agree with him there but i could go on and on about the things that should have been put in the Harry Potter movies or things i felt deserved more attention (like Fred's death in the final battle). I mean come one that's a pretty important character also they didn't even tell you that Tonk's was pregnant or that she even had the baby till after they were both dead and Harry is on his way to the woods to fight voldemort. But I digress I know there excuse for these things not making the cut is due to the play time but come on now Harry Potter could have been 5 hrs long and people would be dying to sit through it. I don't know about you but for me I don't care how long a movie is as long as its done well and i would much rather have a long movie then one with holes in it. I also think that directors and casting directors should be made to read the books so they can cast the character properly i love the Twilight series but I would have cast Bella and Rosalie differently based on the description in the book I would have cast Edward differently as well. But although Kristen Stewart's stuttering and awkwardness is really hard to watch the movies are worth sitting through it. I just hope that in the ending of Twilight they don't do what all the movies are doing and rush through the battle. But I'm sure they will and i will be left feeling unsatisfied like when i left Harry Potter part 2.