Who the PEOPLE OF THE BOOK are
Somewhat mixed understanding regarding this so I hoped to pass on some knowledge...hope it helps. The people of the book as stated in the quran are still the same Christians and Jews of now. Nothing has changed except time.
Consider the following from Surah Nisah
Qur'an 4:171-173 (The Women)
O people of the Book! commit no excesses in your religion: nor say of Allah aught but truth. Christ (Maseeh) Jesus the son of Mary was (no more than) an Apostle of Allah and His Word which He bestowed on Mary and a Spirit proceeding from Him: so believe in Allah and His Apostles. Say not "Trinity": desist: it will be better for you: for Allah is One Allah: glory be to him: (for Exalted is He) above having a son. To Him belong all things in the heavens and on earth. And enough is Allah as a Disposer of affairs.
See how Allah is addressing "people of book" warning them NOT to believe in the father, son and holy spirit i.e. trinity? This belief hasn't changed since hence you CAN get married to someone who holds such a believe as they ARE the people of the book.
It is easier for someone of such faith to understand Islam and notice the similarity between his faith i.e. Christianity/Judaism and Islam ending up believing in One True God.
where does it say that u can get married to the christians and the jews????
yes it was once allowed. but it was forbidden at a later stage and details can be found out in the hades.