2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/169931We define the reduced Khovanov homology of an open book (S,h), and we identify a distinguished "contact element" in this group which may be used to establish the tightness or non-fillability of contact structures compatible with (S,h). Our construction generalizes the relationship between the reduced Khovanov homology of a link and the Heegaard Floer homology of its branched double cover. As an application, we give combinatorial proofs of tightness for several contact structures which are not Stein-fillable. Lastly, we investigate a comultiplication structure on the reduced Khovanov homology of an open book which parallels the comultiplication on Heegaard Floer homology defined previously by the first author.Added Proposition 1.4 regarding non-fillability. Expanded Lemma 5.1 and corrected its proofGeometric TopologySymplectic Geometrytext