yet to vietnam. which is why, when he took a detour to write "working," it caused -- well, heart burn. >> i want people to have some idea of what it is the i do, how it is to research this type of book. chris: caro fans may not be happy he took time from finishing the story of lbj, but it is fascinating to learn how he goes about his master work. caro says he learned about research from the his editor at newsday back in the '60s. >> this guy looks up at me, and he says, just remember, turn every page. never assume anything. turn every page. chris: it's advice he's followed researching lyndon johnson. you walk into the lbj presidential library, and when you look up at the documents section, what do you see? >> you see at that time 32 million documents. they had 40,000 boxes, each of these boxes holds about 800