Hugh,
In addition to the information in this article I would like to mention that there are many free Kindle books at Amazon as well at archive.org that are in the public domain. You do not need a Kindle (or Amazon Prime account) to download and read these books, you can read them on your laptop/desktop computer with the free downloadable Kindle PC reading app from Amazon. If you use the shipping option that gives you a 99 cent credit usable on Kindle books or digital audio products it has been my experience that the length of time between ordering and arrival has not been any different than the fastest free option, and you can use that credit on Kindle books.
Another Amazon feature that I use numerous times daily, is the Send-to-Kindle app. This particular article in fact, like many on Survival Blog, I view on my Safari web browser and use the reader view and on the pull-down ‘file’ option I “save as PDF” to a folder on my computer. Once there I “Send-to-Kindle” to my portable Kindle Fire on which I’ve got an encyclopedia of knowledge. Saved as PDF files also makes them easy to print out and placed in that binder we all have.
Lastly, and most importantly, the section on Amazon reviews In Sarah Latimers’ article is very excellent and perhaps the most valuable information of all. In fact, I often read one-star ratings just for entertainment: “I rated this one-star because I got it as a gift and I already have one”. – Mr. T