If you have a paid Prime membership (the free student ones don’t work, the $39 student ones will), you can borrow one book per month for free from the Kindle Lending Library.
I’ve identified a couple catches. This only works if you have a Kindle (the Kindle apps for iOS / Mac / etc. won’t work as far as I know). Also, Amazon has made it a little difficult to browse the books that are available for free. However, I found a post describing a workaround for the second problem. Seems to work great.
- Go to www.amazon.com .
- Select “Books” in the drop-down menu for the main search box.
- Leaving the search box empty, click on the “Go” button.
- Click “Kindle Edition.”
- Scroll down on the left hand side and click the “Prime Eligible” filter.
- Pick a book and get reading.