Let's make it clearer for your appalling narrow grasp, laddy: it doesn't have to do with how fast you read it. You may read the book in half an hour for all I care. It's not how you receive it, it's how you make it.
It has to do with amount of information, the time needed to make the ideas, emotions & events at least coherent and believable, and pacing.
Now: Moore's work is famous for being just perfect in all these so complex things together. It took a whole book to make it all a working and complex universe.
If you give the movie, based on this really peculiar and detailed book, the same as TDK got, you're giving the audience a very, very tight synthesis.
I understand that all you want and need is the most simple digest they can offer you, and fast, but even you may understand that people can think otherwise and have other kind of expectation.
I suppose, of course.