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Using first-principles calculations, we study the structural, electronic and optical properties of the monolayer, bilayer and trilayer germanium monosulfide GeS. The results reveal an indirect semiconducting band gap for the monolayer and trilayer GeS, whereas the gap is direct for the bilayer GeS. Both the generalized gradient approximation and the screened hybrid functionals assess a decrease in band energy as the number of layers is improved. Furthermore, due to the high buckling of lattice structures, the optical spectra show significant degree of anisotropy. The number of layers engineers key optical parameters including the refractive index, the reflectivity absorption and provides the layered GeS with excellent absorption in the low energy region, namely the visible and UV range of the electromagnetic spectrum. Accordingly, 2D hexagonal GeS few-layers can be used as a highly promising material in the optoelectronic, ultraviolet optical nanodevices and photovoltaics. • Layered GeS materials are studied to control intrinsic optoelectronic key parameters. • The increase of layers numbers leads to a transition from indirect to direct band gap. • Optical spectra show significant degree of anisotropy. • The absorption spectra occur at visible range and UV light of solar spectrum. • Few-layer GeS are promising for solar cell donor and photovoltaic materials. [ABSTRACT FROM AUTHOR]