[Margaret Pilkington]

Yes, there are sites where you can download books free of charge,
The Kindles rarely come with any books on them unless they are second hand and the previous owner has left them on for you.(I suspect the ones in Tesco were the Barnes and Noble NOOK - they come with 100 titles pre loaded - they tend to be the classics Jane Eyre, Wuthering Heights...that kind of thing)
Amazon have had some books recently at twenty pence a throw.......and you can read a bit of them before you buy them, but at twenty pence...heck you can't buy them in the charity shops for that.
I believe that you can also register e-readers with the library and borrow e-books from the library, much as you would do with any library book.
I never thought I would take to the Kindle, but now I hate being without it.