In the chapter special emphasis is put on interaction of x-ray polarized and nonpolarized radiation with hexagonal BN (h-BN) crystal. h-BN is one of the most anisotropic layer compounds. sp² hybridization controlling chemical bonding of boron and nitrogen atoms causes strong anisotropy of the electronic and atomic properties along and perpendicular to the atomic layers in the crystal. Near the B and N K shell ionization thresholds the dielectric tensor in h-BN demonstrates sharp variations with photon energy and results in intriguing optical properties of the compound. X-ray absorption near the thresholds is strongly influenced by the short range order parameters of the layers and demonstrates the pronounced "molecular" properties. The following chemical, structural and optical aspects of h-BN are discussed in more detail: 1) crystal structure and chemical bonding; 2) ground-state properties, band structure and density of states; 3) quasi-atomic properties of x-ray absorption and inner-shell photoemission; 4) x-ray optics of h-BN; 5) orientation and polarization effects in the x-ray reflection, photon scattering and absorption; 6) x-ray Polaroid.