Both are about two male leads and their strong bond (in reality it is a romantic relationship but has censorship). Both are wonderful stories about eternal love that lasts through much hardships and trials. Both semes are questionably evil (this is debatable for spoiler-y reasons) and both ukes are kind and good at heart. Both have a good amount of mystery, suffering, comedy, tragedy, (b)romance, and fantasy. If you really enjoyed H2A then you would absolutely love Heaven Official's Blessing (go and read the novel!).