Cast the adaptation of your favorite books

If you can tolerate the thought of having your favorite books adapted to the silver screen, who would you like seeing take the lead roles? Do you have any actors in mind when you reread the book? Or do you try to envision the character with an unknown yet known face?

Right now, I'm listening to the audiobook of Fahrenheit 451 read by the author himself. I know that for the past 10 years or so Mel Gibson has been holding onto the film adaptation rights and has constantly threatened to make a remake. These rumors come and go and the remake still languishes on.

One rumor had it that Tom Hanks would fill in the Guy Montag lead.
The rumor was published: 2007-11-10. Three years ago! Now that's a half century in Hollywood terms.
http://www.cinemablend.com/new/Hanks-May-Play-Montag-6894.htm

I really like Tom Hanks. He's got the acting chops but it's too much of a safe casting for my taste. Too bland i guess.

So... who would you cast as the protagonist in the film adaptation of your favorite novel? Your favorite biopic? Your favorite nonfiction adaptation?