I was given a book by an author friend I know but I'm thinking of returning it.
Why would you return it?
After reading that book I was mentally distressed for a while. I don't want to have it around me so I think I should return it.
It's understandable that the book may have upset you but they gave you that book as a friend so you shouldn't return it. You should just put it away and not read it anymore or even consider regifting it to a family member.
I feel like I need to destroy copies of it instead.
I don't think you need to go that far, just return the book if it's causing this much distress. I'm sure your friend would understand.