A modular troffer-style fixture that is well-suited for use with solid state light sources, such as LEDs, to provide a surface ambient light (SAL). The fixture comprises two structural components: a housing subassembly and a lighting subassembly. These two subassemblies may be removably attached to operate as a singular fixture. Many different lighting subassemblies may be compatible with a single housing subassembly and vice versa. The housing subassembly comprises a body that is mountable to an external structure. The lighting subassembly comprises the light sources and optical elements that tailor the light to achieve a particular profile. Electronics necessary to power and control the light sources may be disposed in the housing subassembly, the lighting subassembly, or both. Various mount mechanisms may be used to attach the fixture to a surface such as a ceiling or a wall. Multiple fixtures can be connected serially to provide an extended continuous fixture.