That's a *really* neat twist. I immediately begin wondering if the reality of monsters is genuinely new, or if it's something that goes in cycles. So, yeah, *some* of those old books will have accurate information -- and some will be flat-out superstition. Hope you picked the right ones, bud, because that door isn't going to hold the ghouls back for much longer.
I look forward with great interest to game reports and more setting information.