The new Adams Street Branch of the Boston Public Library, which opened last summer in the working-class municipality of Dorchester, is pleasing (if a bit of an odd duck), a work of inventive geometries that fits neatly into its low-rise context. The library’s quirky form was the product of a lengthy community-design process, one that forced the architects, Boston-based NADAAA, to rethink its original proposal for the building.