Slaughterhouse Five or Do We Have Free Will?

I've just finished reading Slaughterhouse Five by Kurt Vonnegut. Has anyone else out there read it? Can you explain it to me?

It was interesting on a number of fronts:

• Definitely not a front-to-back narrative. When the narrator dies, he simply continues narrating the book. You hardly even notice.
• Calling WWII the Children's Crusade resonates with our current conflict. When I see lists of the dead, 95% of them are far younger than I am.
• It questions the existance of Free Will. Aliens teach the narrator that all of time is already laid out and visible, if you know how to see it. In fact, in the entire novel, the protagonist seems to make only 1 decision, to marry a woman no one else wants to marry. Everything else in his life seems to be a matter of being in the right/wrong place at the right/wrong time and being accepting of what happens.

I am a free-will/personal-responsibility sort of person myself. Maybe it's a matter of wanting to feel in control, or of not being cut of from opportunity. Thoughts? I'd love to hear....