I suspect your parents are set in many of their ways by now. When did your parents grow up and under what circumstances? For example, if money came hard in their family, then they won't forget. Older folks tend to be more conservative than younger ones when it comes to money. My mother is 85, and although she has plenty of money now, she still is very careful with her finances. Yes, embarassingly careful sometimes!
And books are very valuable to some people. There were days when the number of books in a family home were calculated in determining a family's social class!
Just like you probably don't like unsolicited advice from them, they are likely to feel the same and even double.
I know it won't be easy, but you are going to need to be patient with what you perceive as their quirks. That's my take on the matter, anyway.
I'll be interested in hearing what other folks have to say.