These days, Almost exclusively.

I went through a phase of buying an enormous number of used paperbacks, before I had my first Kindle or iPad. At one point I had almost the whole Wheel of Time stack, along with stacks of other titles. It just wasn't sustainable. I don't have the space for all those books, nor the time to dust them, nor the money to buy books that I may only read once.

These days, I'll only buy a book if I want to study it, or to keep it as an object, because I'll still probably end up reading it digitally, or listen to the audiobook.