I can’t play their ebooks on my Kindle Fire, so I buy from Amazon instead. This is like the VHS-Beta wars of the 80’s.
They led the way with the Nook, but they didn’t keep up. Both of my Nooks have had issues with the e-ink screen getting small places that quit working. Their website search engine and book recommendations compared to Amazon’s is terrible. I recently gave up on them and my Nook device, and downloaded the Kindle app to my iPad.
I use Calibre which lets me convert just about any ebook format to mobi (Kindle format) and its free!