Does anybody know why they are so hard to buy from outside the US?

International shipping of individual books has become very expensive. Within the US, media mail provides an inexpensive option for authors.

The loss of the bookdepository is a big one.

For some modern books you can get a digital copy.

I almost want to start a website dedicated to people bringing books on the plane with them when flying, but I'm sure that would light every single alarm bell the TSA has ever dreamed of having.

Oh, interesting. I still have Amit's book here on my shelf.

Though I see this author has also given up work on this project. And they are extremely expensive in Europe. At least Amit Singh's I could just grab on local Amazon. Levin's aren't available here.