“As a founding editor of n+1, the literary magazine whose vocal fan base belies its twice-yearly 7,500-copy print run, Keith Gessen and his colleagues have assailed other publications they believe have squandered their eminence (The New Republic) or never merited it (McSweeney’s and anything else associated with the writer Dave Eggers). And the idea of literary fame is central to “All the Sad Young Literary Men.”