In spite of continued research efforts over the past several years, the understanding of the magnetic order and electronic properties of U3O8 has proved elusive so far. Based on published neutron magnetic scattering data and DFT-based methods we show that 1) anisotropic effective spin interactions induce a collinear magnetic order in this layered system, with antiferromagnetic (AFM) coupling both in-layer and between layers, 2) charge localization transforms the in-layer triangular lattice of U atoms into a slightly distorted honeycomb lattice with Néel-type AFM ground-state while relieving the initial AFM order topological frustration; the in-plane long-range order is stabilized at finite temperature thanks to the interlayer coupling, 3) the latter arises from a superexchange mechanism mediated by the oxygen atoms bridging the layers, and 4) spin-orbit coupling has a strong impact on the band gap and electronic properties of the system. Recent optical absorption measurements strongly support our results.