I liked this movie when it was released but at that point in time I was still a teenager. There was a lot about this movie that went over my head back then but understand it more now than ever. As a matter of fact in recent years we've seen more shifts in late night TV. Jay Leno retired twice, the Tonight Show essentially has gone through three hosts since at least 2009. After Jay, Conan O'Brien and after Jay again Jimmy Fallon with both Conan & Jimmy having hosted Late Night.
As we see in this movie and of course in reality Letterman moved over to CBS to host their Late Show after failing to get his dream job at Tonight. It was fun to see the positioning of both Letterman, Leno and all the players who made their pitches. In terms of what happened since Letterman retired from hosting Late Show.
If I recall correctly at times Comedy Central has shown this film. Now while this story involves two comedians at least, this doesn't strike me as a comedy, more as a drama. Some of what we see aren't meant to be funny although we see the actors who portray these comedians portray their roles adopting each comedians mannerisms. The comedians tell their jokes for the most part and as a result it seems the drama is portrayed by network executives & agents.
BTW, the scene above shows Letterman after a show lamenting how the crowd responded to him. He's definitely hyper even with a message to comedienne Sandra Bernhard that starts this scene off right. It's amusing, but an important part of this drama.
ALSO, this book has a sequel which revolves around "the late shift" that occurred in 2010 again with NBC's Tonight Show. After 7 months hosting NBC's signature late night franchise O'Brien was pushed out in favor of a returning Jay Leno. I'd like to see that adapted into a film in the near future.