An excellent companion to the ongoing History of Late Night series is the Playboy Interviews collection Late-Night Talkers, available for Kindle. The collection includes Cavett, Leno, Stewart...many notables except, unfortunately, Johnny Carson.
The David Letterman interview from the October 1984 issue is a real winner, though. You get Dave as the 12:30 show is taking hold but the sting of past failures is still strong. His comments are often funny but also insightful. There are some moments of sincerity and vulnerability, too; at one point he expresses guilt and shame about not realizing what the Vietnam War did to his contemporaries who served (he got a favorable position in the draft lottery).
Asked about guests who he didn't like--remember, this is only 1984--he gives this answer:
"The only guest who really bothered me was Andy Rooney--and he was especially disappointing, because here was a man I'd admired for a long, long time. Years before 60 Minutes, Andy had done a series of news specials that I think represented American television at its best: entertaining, intelligent--absolutely state of the art stuff. But when you actually meet the guy, you quickly discover that he doesn't just appear to be a nasty curmudgeon, he is a nasty curmudgeon."
The questioner asks what guests excited him to have on the show, and Letterman responds, "This may sound crazy, but I found myself really looking forward to meeting Johnny Bench."
Asked if he watches much TV, Dave says sometimes if he likes something he will try to catch it, and he mentions Cheers. Then he adds, "But I must say I do enjoy watching The Love Boat. To me, that's American TV at its finest."
The interviewer wonders, "Because it's so bad?"
The reply: "I won't go on record saying The Love Boat is bad TV. It's solid American fare, and there's no mystery as to why it has succeeded. Every week, people from other television shows are thrown together in what's presented as a glamorous circumstance. And I get a kick out of that."