I mostly do not know what book I want to read after the current book. I am an eclectic reader and vary my reading genres all the time. I read three Westerns last and am reading Science Fiction now. Before that I was reading a Biography. Having a lot of books on allows me a larger selection to browse through. Sort of like my own bookstore.
I bought a Nook Tablet and returned it. I find it ridiculous that a 16 gig Nook Tablet allows me to side load only one gig. I do not think I will be buying 15 gigs of books from B & N.