I know that initially, an important consideration in my purchase of an EBR was whether or not I could read library books on it. The reality of it is that the only library ebooks I've borrowed were for testing purposes with the Kindle. I find that my local library has few ebooks that I'm interested in. And the few they have are on long waits.
I have enough to read from multiple other sources such that the library issue has become a moot point for me.
And I can always use the iPad to read a library ebook if I choose to wait for something they actually have.. and decide not to put it on the K3. Shucks, I might even actually borrow a real paperback book.