The Barnes & Noble ebook (styled “nook”) is developed by American book retailer Barnes & Noble , B&N ebook have Barnes & Noble’s eReader DRM, sometimes called Secure eReader format.  all other device doesn’t support B&N ebook drm,   so user can’t read these books on Kindle, iPad, Sony e-reader unless remove DRM protection first.

this is tutorial how to remove B&N DRM, detail at

How to remove DRM from Barnes Noble B&N ebook?