you can use calibre and get books from many other sources. my current favorites are Smashwords and Baen Books. I haven't done it, but understand that library books can be downloaded and converted using calibre also. I have had one K1 for over 18 months, a second one for 9 months with absolutely no regrets or breakage. the only thing I have had to do is rest them a few times.
when I was in the hospital having knee surgery, the morphine didn't work. I went 36 hours in absolute agony. I "read" (didn't absorb a damn word) the entire time just to keep my brain busy. the battery lasted that whole time