Well, first off, whenever asked about a History book, I almost always point to the most appropriate one of Colin McEvedy's Penguin Atlases. I believe the one in question here would be the New Penguin Atlas of Medieval History

I see, thanks. I'll look into it.

@William If that's the question, definitely go to Geneology. They would be the experts in searching old records for information about a specific non-famous person.