Who are the ahlul kitaab. there are three books before Al Qur'an : Taurat, Zabur and the Injeel. Which book is Allah referring to as Kitaab because He did not say ahlul Kutub?

There are more than three books before the Quran, all the Rusul (313) were sent with a book. Quran tells about the book of Ibrahim even though we don’t know its name.

Ahlul Kitab refers to the Jews and Christians as it is commonly used, since followers of other books have now become extinct.