The approach is roughly chronological, beginning with Charlie Chaplin and ending with Apatow, and the connections that Austerlitz makes are quite interesting.
But I just lied. The book doesn't end with Apatow. In fact, my favorite part of it comes after Chapter 30. There are almost 100 pages of "Short Entries" on various actors. These entries make for fascinating reading, especially when I agree with it. How could I not love a book whose author says, "Rio Bravo is not only the finest comic western ever made; it might also be the finest western, period." Take that, Brian Garfield!
The book's actual conclusion, and another thing that the docile readers of this blog won't care to argue with, I'm sure, is a list of the "Top 100 American Comedies."
This is a really entertaining and interesting book. If you care about comedy or movies, you'll certainly want to have it in your library.