Azobenzene is a molecular photoswitch of trans ↔ cis type. Shifting between the isomers with light enables various transformations and control over numerous properties of systems ranging from macromolecules 1-3 through interfaces to solids. In (soft) condensed matter systems, such as azobenzene-containing self-assembled monolayers (SAMs), micelles, , liquid crystals or crystals, azobenzene units are, in general, coupled to each other. This coupling manifests itself in spectral changes with respect to the corresponding "monomer" case, e.g. dissolved azobenzene-containing molecules in solution. The alteration of electronic structure with assosiation / aggregation of azobenzene chromophores, responsible for the observed spectral changes, can be conceptually described by the molecular exciton model, which has been known for more than half a century, especially in the context of molecular crystals and molecular dimers. The simplest variant of the exciton model is based on the assumption that the coupling between chromophores can be described by point dipole interaction of transition dipole moments, the so-called point dipole approximation (PDA) or point dipole model (PDM). Whereas this approximation captures the crux of the excitonic problem, the real life situations may be more difficult than predicted by PDM or even involve effects not accounted for by this simple treatment, such as charge transfer. The most accurate way to take them into account is to calculate the electronic structure of the aggregate from first principles.