By about paragraph five, I was asking myself approximately the same question you got from your last therapist. Do you have an answer for that? Maybe pinning down your motivation to reduce will lead you to a method to reduce?
If the goal isn’t so much to buy fewer books or get rid of books but to get through more of books, I’ve listened to audio books from the library to accomplish that. I feel like it generally takes me longer to listen to a book than to read it. However, I can listen to a book during times when I can’t read a book, such as while cooking, cleaning, or driving. This has the added benefit of making me less annoyed about having to do these activities.