Leanpub books & courses all have both a minimum and a suggested price, and you choose what to pay.
If the minimum price has been set to free, to choose to pay for free, you drag the "pricing slider" to the left, until it says "Free!".
The pricing slider is at the top right of the page where you buy a book or course.
So, if you see something like this:
... you can drag the "YOU PAY" pricing slider to the left, and you will see something like this:
Please note that we make it easy to get refunds within 60 days of purchase, so if you have been charged, you should be able to get a refund with a couple of clicks, and then you can go back and get the book or course again, this time for free. Here are the refund instructions:
Here is a short article that should help explain our variable pricing model in a bit more detail: