Yes, that is a function of the book provider. Also one can read many books free for an hour in a B&N store. Often that is enough time to read an entire title otherwise one can return another day and continue reading.

I've never read a Kindle book. I am very pleased with my Nook readers. I have 2 - an original and a Touch. IMO which product is best is more about where you wish to purchase content and what formats your local public library supports. Kindle and Nook have similar features. The entry level Kindle has advertising that can't be turned off.