Complex sentence: Another motif is an old apartment building whose image appears at moments when Seth questions his search for Kalo, whose neglected work, to Postema, is similarly "unpreserved, unnoticed, and left to decay".
Split into simpler sentences: Another motif is an old apartment building, the image of which appears at moments when Seth questions his search for Kalo. For Postema, Kalo's neglected work is similarly "unpreserved, unnoticed, and left to decay".