Rare book from 1715 written in Italian

as long as it doesn't have any major physical damage, I would think it might have some decent value. You might consider consulting with
somebody at specifically a Catholic antiquarian book place. Generally I imagine that WON'T be the type of thing they could advise for you over the telephone or via email; but in an onsite visit with them.

I used to work in Public library reference desks and I was often astonished with the depth of material published by/ for the Catholic Church.

Best of luck.