I've been stealing my aunt's books for years
How were you able to steal her books?
She was a huge book lover and she usually left her books around the house
Stealing is legally and ethically wrong, especially when the victim is a family member. I think that you should return all of these books, and possibly talk with your aunt and try to make amends for your actions against her.
None of your business.
I understand if you don't want to talk about it any further, but I have to reiterate that it is wrong to steal from family.  You should return those books to her, even if you don't say anything.  It is better to merely borrow things than to actually steal them.