Does the adam&eve story make any sense?

i dont understand how christians are supposed to hate incest yet the bible says humans came from two people who werent married by the way... i dont get it..so your telling me adam and eve had sex then had babys and then they had sex and even had sex with their parents.. i dont get how they didnt come out disfigured and retarded and i also dont see how god let this all happen and watched it too...and the thing with the apple is beyond me why god didnt want them to eat it but put it there anyway is retarded