The paper by Tawinan Cheiwchanchamnangij and Walter R. L. Lambrecht presents quasiparticle self-consistent GW calculations of the band structures and effective mass parameters for bulk, monolayer, and bilayer MoS$_2$. The calculations include excitonic effects within the Mott-Wannier theory, achieving quantitative agreement with experimental exciton gap energies at the K point. The A-B splitting in the monolayer arises from spin-orbit coupling, while in the bilayer, it is a combination of interlayer and spin-orbit coupling effects. The study also discusses the transition from an indirect to a direct band gap in monolayer MoS$_2$, which contrasts with recent G_0W_0 results. The excitonic effects are estimated using the Mott-Wannier theory, showing good agreement with experimental data for the A and B excitons. The findings highlight the importance of excitonic effects in understanding the optical properties of MoS$_2$.The paper by Tawinan Cheiwchanchamnangij and Walter R. L. Lambrecht presents quasiparticle self-consistent GW calculations of the band structures and effective mass parameters for bulk, monolayer, and bilayer MoS$_2$. The calculations include excitonic effects within the Mott-Wannier theory, achieving quantitative agreement with experimental exciton gap energies at the K point. The A-B splitting in the monolayer arises from spin-orbit coupling, while in the bilayer, it is a combination of interlayer and spin-orbit coupling effects. The study also discusses the transition from an indirect to a direct band gap in monolayer MoS$_2$, which contrasts with recent G_0W_0 results. The excitonic effects are estimated using the Mott-Wannier theory, showing good agreement with experimental data for the A and B excitons. The findings highlight the importance of excitonic effects in understanding the optical properties of MoS$_2$.