If you've had a Samsung before, you should be close. If you haven't, Samsung has its own version of Android. Lots of Samsung's own apps plus Google's Play store.
The 7 will come with Marshmallow. You can disable much of what you don't like and set up the phone your way.
If you wish to read on it, Most of the good reading apps are reviewed here and should work on the Samsung. Take your pick.
Marshmallow has a strange ext. SD card issue with some phones. The card has to be formatted for either media or data. Books don't seem to be included in Media.
If you format card for data, pictures, videos, etc. will not write to card, so check out all info before buying.
http://androidforums.com/forums/android-news-talk.12/
http://forums.androidcentral.com/
Both these sites have very good info on the Samsung and the card issue. It could be that Sammy has fixed the card issue on its own phones.