pages. that's the only time the i felt like turning around and going home. chris: caro says he has one big rule when interviewing. your notebooks are filled with a notation -- [laughter] >> yeah. chris: what does that mean? >> shut up. [laughter] people have a desire, a need to fill in silences. if you could just make yourself shut up, often they'll tell you what you want to know. chris: then there's writing. caro remembers what a professor at princeton told him. >> you're never going to achieve what you want to achieve, mr. caro, unless you stop thinking with your fingers. i knew exactly what he meant. it was so easy for me to write. i didn't think things through. chris: which brings us back to his final book on lbj which is about a third written. caro took us into his office. >> this is the outline to have the rest of my last volume. from here to there to end of the book over there. chris: he writes several drafts