I suppose to an extent I play it in my head as a film but it tends to be for only certain parts rather than for the whole thing. It might be more accurate to say that I tend to develop an image of particular characters in my mind (maybe like a composite sketch for identification purposes) than to imagine them acting out the story. I don't know if that says anything much about how smart or otherwise my brain is but that's the way it normally works for me.
Does anyone see it the other way round? I'm just reading a Tom Clancy with Jack Ryan in and I can't help but see him as Harrison Ford.