Oh boy, I hope they do it justice. It's a great book (I just finished reading it). Somehow hearing John Singleton is directing does not inspire much hope in me. Joaquin Phoenix is a good actor, so maybe he will do well. I liked Liev Schreiber better though (he played John in The Sum of All Fears).
What worries me most is it's a long book with a lot of character building. Trying to cram it into a two hour movie...