Yes, the story features obscure books in forgotten tongues, secret brotherhoods, exotic locales and clever puzzles, but Fasman comes across as a novelist genuinely interested in unraveling the convention of the thriller, and he gives his tale a delightfully and successfully postmodern flavor. And rather than presenting obscure knowledge as valuable only because it gets you things, he is far more interested in showing how physical things lead to knowledge.
Unlike most arcane thrillers, which are ultimately mundane thrillers gussied up with the occasional info dump, The Geographer's Library makes an effort to get readers off their intellectual duffs by presenting the artifacts in catalog format, separating them from the narrative and demanding that they be seen as elements of a puzzle rather than props in a set piece.
The arcane thriller is typified by Umberto Eco's The Name of the Rose, and Foucault's Pendulum also fits the criteria. Also, to some degree Lev Grossman's Codex, which I read recently, and a favourite, Arturo Perez-Reverte's The Club Dumas. All of these put Dan Brown to shame. Are there so few books (and such little interest) in this niche?