[fjtorres]

You may want to check your Amazon account settings.
You may have accidentally signed up for Kindle Unlimited.
Or, if you're a Prime subscriber, be using your Prime Reading privileges.

There are several ways to read Kindle books for "free" on the Amazon store that require you to return books befire downloading more.

This is in *addition* to the books priced at zero as a temporary promotion or, less common, permanently. There's still thousands of those at any one time but there is well over a million of the Kindle Unlimited titles.

Downloading one of the Kindle Unlimited books is all it takes to enroll in a 30-day free trial of Kindle Unlimited, which lets you download a queue of ten of those titles to read. Once you've finished one, you return it and downkoad another. No limit on how many you can read as long as the subscription is active. Of course, once the free 30 day trial is uo, you get charged $10 each month. You may find the rate acceptable or not. Enough people do that Kindle Unlimited (by itself) is a bigger business than most other ebookstore combined. If you don't find it acceptable, make note of the renewal date and cancel the subscription. Then read as many of the KU titles as you can in your free month.

You need to read the description near the buy button to know what you're getting.
It's been a whole new ballgame since 2014.

(Prime Reading lets Prime subscribers check out a subset of about a thousand KU titles without being subscribed to KU. The titles are supposed to rotate every three months or so. Just another Prime Perk, of which there's a whole bunch.)