I was also interested to see if the film has affected my mental picture of the story, or more particularly, the characters.
Interestingly, it has and it hasn't. Characters like Gandalf I've always had so clearly pictured that it would be hard to think of them any other way - and thankfully, the casting of the films was so spot on that it didn't offend me, either.
Others, like maybe Legolas, or even to an extent Frodo, I don't think I had as crystal-clear a picture of, so as I read, they are taking on some of the attributes of their film representation.
Has anybody else experienced a similar or opposite reaction, we wonders, we does?