Intermarrying among Adam and Eve's children
Question

                Asalam Alaikum?
I have no doubt whatsoever, but these kind a things come to mind. Whem Adam and Eve 
bore children, I assume their children got married among themselves. Isnt marrying 
between brothers and sisters haram in the Quran? 
Can you recommend a good book(s) on Islamic Law covering every and each aspect of 
Life? Thank you very much for the generous work for the sake of Allah. Thanks.
Praise be to Allah.wa alaikum us-salaam wa-rahmat ullaahi wa-barakaatuh
All Praise be to Allaah.
As long as you are confident in your heart about your belief, no such insinuations will hurt you (inshaa' 
Allaah). If a doubt strikes a believer or something appears to him as a conflict between different textual 
sources of Shari'ah, he must believe that indeed for such doubts there are true answers and for such 
apparent conflicts there are solutions even if he doesnt know it or is unable to find the right answer 
himself. However, a person should not collect all the doubts in his heart and worry about the 
complexities and leave aside the learning of useful knowledge. This is because it is incumbent upon a 
Muslim to learn and know things which have been clearly described (Muhkamaat) in Shari'ah so that he 
may be able to repel the doubts. 
Regarding the question you have asked, it is a known fact that legislation differs from one Shari'ah to 
another, while the principles and beliefs remain the same in all of them. So, making of portraits was 
allowed in the Shari'ah of Sulayman (peace be upon him) but is prohibited in our Shari'ah. Similarly, 
making prostration of salutation was permitted in the Shari'ah of Yusuf (peace be upon him) but is illegal 
in ours. Also, war booty was prohibited for nations before us but it is completely legal for us. The 
Qiblah of people before us used to be towards Bayt Al-Maqdis, but for us it is towards Ka'bah. In a 
similar way, marriage between brothers and sisters was permitted in the Shari'ah of Adam (peace be 
upon him) as opposed to those that came afterwards. The following is a clarification on the issue by 
Haafidh Ibn Katheer, who said: 
Allaah allowed Adam (peace be upon him) to marry his daughters to his sons for necessity. Every 
couple used to have a boy and a girl. Hence, he married the girl of one couple to the boy of another. 
This is said by Suddi regarding what has been narrated by Abu Maalik and Abu Salih, from Ibn Abbas, 
by Murrah from Ibn Masood and by other companions of the Prophet  (peace be upon him) that 
Adam did not have (in his grandchildren) a baby boy unless it was accompanied by a girl, so he married 
the male of a couple to the female of another, and the female of a couple to the male of another.