If you have an Amazon Prime account (you know who you are), there are several Kindle book related benefits recently added. Authors who have books published through Amazon for the Kindle have an option to make any of their books available for borrowing by Amazon Prime members. This means once a month you can borrow certain books and read them for FREE.
This is in addition to FREE 2 day shipping on most items and thousands of FREE movies and tv shows.
So if you are a Prime member. Enjoy! Of course if you like a book enough to keep it, you can still purchase it. Then it is yours forever!