SOMEWHAT COINCIDENTALLY, I read the first half of this in a club, waiting for a band that first made their mark in the 1990s, the Brian Jonestown Massacre, to take the stage. (They weren't late; I was early.) Different coast, though, and not even quite the same Nineties--the Joe Brainard-esque list that occurs at the book's midpoint begins "Filofax, whippets, Urban Outfitters, snap bracelet," which is not exactly Anton Newcomb territory.
Imagine that the Gossip Girl series was written by Paul Bowles, and you will have a rough approximation of Nineties. It is set in an expensive NYC private school and follows the interactions and transgressions of a small group of girls (á la Gossip Girl) and written in a scrupulously spare style that excludes contextualization, explanation of motive, and moral judgement (á la Bowles). The absence of commentary and interiority is even made visible in the text, as white space.
Quite a different vein from Orange Roses, but complementary in a way, perhaps? Is the unnamed narrator of Nineties the teenaged version of the young writer whose choices and ambitions are contemplated with a certain dry disenchantment in Orange Roses? They seem like quite different people, but no more different than the Kit Moresby of the first chapter of The Sheltering Sky is from the Kit Moresby of the last.