I think this is a complicated topic. There are various opinions.
Some consider only Jews and Christians Ahle Kitab.
Some consider Hindus ahle Kitab too because they interprete People of Book can be any nation who had received Scriptures.
Some believe only Unitarian non-Muslims women are marriageable to Muslim men.
I believe, one should do proper research and consider all the consequences before marrying a non-muslim woman.