For a decade and a half, NBC was a primetime TV powerhouse with a line-up of shows – most of them on Thursday nights – that rivaled anything on TV at the time. “Cheers,” “The Cosby Show,” “E.R.,” “Frasier”  and “Mad About You” were among the huge hits.

Warren Littlefield wasn’t the writer or star of any of those shows, but he was an NBC executive, rising to the role of president of entertainment programing from 1993 to 1998. As such, he was one of the network “suits” involved in decisions made behind the scenes on all those shows plus others like “Friends.”

In “Top of the Rock: Inside the Rise and Fall of Must-See TV,” Littlefield presents excerpts from interviews with the writers, producers, directors and stars of some of the network’s most memorable shows. Although a few people – like “E.R.” star George Clooney – are notable by their absence from this oral history, Littlefield includes comments and memories from Jerry Seinfleld, Jason Alexander, Noah Wyle and most of the “Friends” cast among many others.

There are a lot of intriguing anecdotes here and some pretty funny memories, especially from people like Seinfeld and Alexander.

Littlefield’s book isn’t the equal of “I Want My MTV” or the similar oral history of “Saturday Night Live” from a few years back. It’s just not as comprehensive. But it offers some good backstory.

Some things I didn’t know, or had forgotten if I ever knew, until I read Littlefield’s book:

The script for the two-hour pilot of “E.R.” was really, really old. People interviewed estimate the script was at least 20 years old when it was reworked by Michael Crichton around 1993. One sign of its age: At one point, characters are watching a Boston Celtics game and a player who retired in 1965 is name-checked.

Kelsey Grammer’s drinking and drugging was a huge problem during “Cheers.” It’s also one retold with some humor here as interviewees note that Grammar might pick up a hitchhiker and make the guy his assistant.

Casting almost-was stories abound. Here they include Terry Hatcher for the eventual Helen Hunt role in “Mad About You” and Lisa Kudrow for the Peri Gilpin role in “Frasier.”

NBC scuttled a two-hour Bob Hope special to pay for four more “test” episodes of “Seinfeld.” Someone had to tell Bob. I’m surprised, retrospectively, that Hope was still doing NBC specials by 1989.

The people behind “Cheers” were really, really pissed when Shelley Long left the show but saw the show get a new lease on life with Kirstie Alley. I think they got a better deal.

Littlefield enjoyed actor Bob Balaban’s parody of him so much on “Seinfeld” that he had Balaban play him at a network meeting. Ha!