Ridley Stone Rewards

But how is it related to Ridley?
Would it change the rates of the items if you hold it?
Usually items that specifically have the NPC in the name should correspond in some way.

Well, if you have the book in your inventory (I have been carrying it around for months now), he says "Interesting reading, my friend! Perhaps if you find a Ridley Stone we can talk..."

so yeah, not much, though he does acknowledge you have it. I doubt it has any affect on rewards.