I do not possess a Kindle, yet, but I do buy books online.
Where I live there are three charity shops in close proximity. I visit them every Saturday. I buy adult and children’s literature. Novels, historical books, books of poetry, plays, and biographies of interesting people throughout history. Eg. Abraham Lincoln.
I give the books that I have read to my nieces.
What types of books do you buy, and what percentage were Kindle purchases?
Unfortunately, I don't think I spend more than £100 a year on books. I am mostly reading from the classics Henry James, Austen, the Brontes, Dickens, Balzac, Tolstoy etc. which can be downloaded for free on the kindle. When I do want to buy a book, I check first to see if there is a version for kindle available. I prefer the e-book format for practical reasons (I move house quite often).