I also use the free app Calibre to sort my ebooks and very easy to convert from EPUB (Nook) to MOBI (Kindle) ..... or back. Very useful and free. I keep my ebooks on my computer and copy them right to my Kindle. Hopefully, you can find a nice used reader soon. I have used both Nook and the base Kindle until they eventually failed. (as they all will someday) I am VERY happy that I made a slight upgrade to the Kindle Paperwhite, which is only slightly more money, but offers a lighted background, which is much easier on my old eyes. I have been lucky to find them used on Ebay and such for very reasonable prices. My wife and I both use these with good luck and the battery lasts plenty long between charges. Good luck.