Gallium monoselenide is a typical representative of group III-VI layered semiconductors, characterized by enhanced structural anisotropy. Their specific quasibidimensional structure, consisting of stratified packages bound by weak Van der Waals forces, favors easy cleavage of plan-parallel plates with atomically smooth surfaces, of any (wanted) thickness, up to nanometric. In this work absorption spectra for E C r r II and E ^ C v r (C r -crystallographic axis, perpendicular to the surface of stratified packages) polarizations in a wide energy range by region of the fundamental absorption band of e-GaSe single crystals are investigated. For measurements plan-parallel plate- samples with thickness between 85 nm and 5.4 cm have been used, enabling measurement of the absorption coefficient in the range of 8×106-1.2×10-1 cm-1, with a precision of ~5 % (0.65≤αd≤1.35). Reflection and transmission spectra at temperatures 78 K and 293 K have been examined. For photon energies hn>3 eV absorption spectra at both temeratures display an excitonic structure, as well as two absorption bands determined by direct optical transitions from deep valence subbands. According to the values of respective absorption thresholds, the spin-orbit splitting of the valence band has been estimated. From the analysis of the absorption and reflection spectra, dispersion of imaginary (e1) and real (e2) parts of the permittivity in the energy range 2.0£hn£3.2 eV has been determined. Effect of the polarized light is clearly emphasised in the exciton absorption band tail region, where absorption coefficient is a£5 cm-1 (hn<1.85 eV at T=293 K). By analysing absorption and permittivity e1(hn) and e2(hn) spectra in this energy range, minimum energy band gap, energy positions of the valence and conduction band edges, as well as character of optical transitions for both E C r r II and E ^ C v r polarisations have been determined. Experimental results were interpreted according to band structure calculations for e-GaSe, performed with 2D and 3D approximations.