I was hoping to get a book on Gravina in

Try 

Notizie storiche sulla citta di Gravina (455-1860)

I can't get it for a long time

This is a rare book indeed. Check online bookstores such as Amazon, Book Depository, Ozon, Labyrinth and others for books about Gravina in Puglia. I will try to find it and help you. I have free time, I found assignment writing services for college, use https://ca.edubirdie.com/assignment-writing-services and I do it often. But you don’t sit idle either. Try searching for websites dedicated to tourism in Puglia. It's a bit of an option, but it might work.