I hate to do this but it's not actually "free" but rather is being added to the library of books being offered for free with a new service they just rolled out that normally costs $10/mo, though they're currently and may do so long term offering short free trial periods. If you've already unwittingly signed yourself up and started your trials, be sure to read the books fast and then cancel the service before they start charging through your Amazon account. Unless you can afford the subscription, and want to continue using it and "borrow" other books through it. That's essentially what this is, a paid subscription lending service.