A little while ago Amazon did something dreadful. They started a program called 'Kindle Unlimited'.
It's not a bad deal for readers - at least not at the moment, because for $9.99 a month (£7.99 in the UK) they can read any of the 700,000 books available in Kindle Select. Plus there are free audiobooks to listen to, and about 500 public domain books available. No more to pay in that month. If you are a prolific or even a little better than average reader (4 books a month), that could save you money. There is one downside - books downloaded through Kindle Unlimited will be deleted if you cease to be a member.
For authors, Kindle Unlimited has it's good and bad points.