As a literary format for fictional social satire, Brooks’ method where the main character ages but society doesn’t has some major advantages for both author and reader. The most natural genre for novelists is the lightly fictionalized autobiographical novel, but what it was like to grow up in, say, Westchester County in the 1980s isn’t necessarily all that galvanizing a subject matter in 2013, especially for somebody of satirical bent: hair metal bands really aren’t that funny anymore. They’ve been done. We’re more interested in the author poking fun at what’s going on right now, but an autobiographical character can only live in 2013 for a year.
So, Brooks’ invention is to write an autobiographical novel always set in the eminently satirizable present.
The traditional alternative for a The Way We Live Now satirical novel is to invent a bunch of realistic characters of different ages and different backgrounds and have them interact in a well-crafted plot. But, that’s hard work. Wolfe, for example, only was fully successful at it in The Bonfire of the Vanities. Hence, this Brooks method has promise as a genre that shouldn’t demand as much talent and time from the author as traditional ones.
I presume somebody else in the long history of literature did this before Brooks, but off the top of my head, I can’t think of who.