Haven't read the book, so I can't comment on how closely the stories match, but if ya liked the story, ya might as well go see it the movie.
9/11, Asperger syndrome: these are tricky themes to make a movie about. Also, the book has a rather original format, which might be difficult to translate to the big screen. I wouldn't say the book is a master piece, but it was an interesting and original read. From the reviews I've read I'm not sure the movie is.