I don't buy books if I have any left that I haven't already read. But I read them rather quickly, so the money I spend on books is instead limited by my willingness to shop for new (to me) books.
When I browse the virtual shelves online, I usually throw a bunch of books on a gift wish list and intentionally not buy them myself, so that other people don't have to struggle at birthdays and gifting holidays.
Also, since they were gifts, I get fewer unwanted interruptions as I'm burning through one of those books after the holiday.