Quirkiness is the unusual quality itself — the oddness that makes a person, a place, or a story interesting rather than ordinary. If quirky is the adjective, quirkiness is the name of that flavour. People talk about the quirkiness of a film, a neighbourhood, a shop, or someone’s humour. In magazines and everyday talk it is usually a compliment, or at least fond: we kept going back because of its quirkiness. It is not a harsh word like madness, and it is not as heavy as eccentricity, which can sound like a judgement on a whole life. Though actually, one person’s quirkiness is another person’s mess — the word puts a kind frame around behaviour that is simply not standard. You will hear it more in reviews and friendly description than in formal reports.