The publisher Captivating History has about half a dozen free titles at Amazon, for any customer. Most of the titles are biographies; however, one is about the Hatian Revolution.
If you are a Kindle Unlimited customer, you have a number of additional titles that you can purchase for free.
The audiophiles among you may wish to know that many, if not most, of the titles also have an audio counterpart. They are inexpensively priced--most in about the $5.50 - $6.00 range. However, they will not be particularly long-running, because the ebooks generally hover around the 200-page mark.
Note that I didn't refer to these as "Whispersync deals." The reason is, they aren't Whispersync deals. You do not have to buy the ebook in order to get the audiobook at its cheap price. You can buy them individually or separately, and get the stated price of each one of them. If I'm not mistaken, when you buy an ebook and then later buy the corresponding audiobook, and vice versa, the two will automatically sync up. But this may only apply to ebooks which have a stated "Whispersync narration." Maybe tubemonkey will read this post and give us an unofficial ruling on this question.
For your convenience, here are the Captivating History titles at Amazon, sorted by price, low to high. Note that the titles that are free for all customers are listed first, followed by the ones free only for Kindle Unlimited customers, and then the not-free-for-anyone titles.
https://www.amazon.com/Captivating%2...price-asc-rank.