I dont read online books and still prefer real books, however if I did have a Kindle or like, that would suit me as renting is all I would need.
Once I have read the book, it would not matter if I kept a copy -I rarely read a book twice.
Also I would not read enough in a month anyway to make it worthwhile.
I think it will have an effect on libraries, however there are still many people who prefer the actual book, as I do.