ToAD presents itself as "a Model Reality Kit - not a model for reality but a model of reality". The rules are intended to enable role-playing in nearly any genre through they are written with a strong fantasy slant and the sample adventure is definitively high fantasy.
Characters have many typical role-playing aspects, including race, sex, Abilities, description, and so forth. Skills in the system are referred to as Preoccupations, which are particular Skills the characters finds compelling over the long term. Preoccupations are somewhat like Skills that develop over time, loosely analogous to a more traditional Class though more freeform. Preoccupations have several dimensions that control performance. Combat is generally simple in concept but numerous special situations add complexity.