There are more and more 'old' books coming to the stores. That is wonderful. I saw that diesel-ebooks has 10 books of Arthur C. Clarke.
There are still odd issues with respect to international availability of e-books. I bought 5 books from Julian May yesterday at diesel-ebooks. Kobobooks could not deliver them due international restrictions. I could also buy those books in the Netherlands, but it would have cost me about 30 Euro more
which is 6 Euro per book. There is a Dutch law imposing a minimum price for books, but that does not apply to e-books.
I may do so more shopping because I saw a lot of Larry Niven books as well and I also stumbled on www.jackvance.com
where e-versions of all his books can be bought and they are DRM free.