I have always had the problem of preconceived notions when seeing a film shortly after reading the book from which it was adapted. This doesn’t historically apply to expectations about the look of the characters as many fans typically do. If the character is blond but played by a brunette, or white and then played by a black man, as long as it doesn't change the character or plot of the film, I'm fine with creative casting.
A second example is Wesley Snipes’ casting in Rising Sun, which I talked about at length here. The short of it is, Snipes (for those of you who aren’t familiar – is black) had the challenge of playing a character that was written as a white man and changed to a black man to water-down the film. The ultimate effect was only disconcerting in one subplot that didn’t ring true, but otherwise it wasn’t distracting – only if Snipes had also colored his hair blonde.
So anyway, that’s not that type of preconceived notions I have problems with. My problem is with overall familiarity. If I'm very familiar with the book and plot, I find myself bored if the film is faithfully adapted. It is akin to marking off a checklist of events that you expect to see. The effect is to remove all anticipation, wonder, excitement, and suspense. You know what is going to happen to the characters, and are actually disappointed when it happens exactly as scripted.
High Fidelity was the first time I remember the effect crippling to my enjoyment of the movie. I had finished Nick Horby's excellent novel about two weeks before I went to see the film adaptation starring John Cusack. Critics and audiences lauded the movie for its brilliance, and my expectations were high going in. Unfortunately, I found myself unable to get out of checklist-mode; the screenplay was so loyal to the book (and why wouldn't it be -- it was a great read and easily adaptable to film) that it felt like reading the book again, this time visually. I do enjoy rereading books from time to time, but I don't ever reread them back-to-back.
Direct "loyal" adaptations from books are usually much worse than "loosely adapted" or "based on" or even reboot concept for my interest level. It doesn't matter how much I enjoyed the book, the film just plays out as somewhat tired.
I have found that time heals all wounds. The cure for this problem has demonstrated to be either (1) don’t read the book before seeing the film – although the desire to read the book after seeing a film is not equal to the reverse instinct, or (2) read the book well in advance of seeing the film. And by well, I mean at least six months, the longer the better. This actually worked wonderfully for me for Harry Potter and the Prisoner of Azkaban, where it had been so long since the book that I had totally forgotten that Harry was his own “father’s” patronus. Because I had forgotten many of the important details of the book, I was able to have suspense again, and I was able in that case to successfully enjoy both book and film on the levels they were intended.
(Slight follow: Lisbeth Salander is already an iconic character, so if you are casting someone who is not a small, slight girl, you are making a mistake.)