|Add to Favorites and Download options|
When you see the Download choice on a Carousel item, you can pretty well bet it is a book. Even if you "purchase" a free offering from Amazon and have it sent to your Cloud Reader, it will appear in your Carousel (just in case you want it on your Kindle Fire too?). Choose Download and it will be downloaded from the Archives (or Cloud) to your Kindle Fire and you will be able to access it (even if you remove it from the Carousel) in your Books area.
See the little down arrow on your Carousel item? This means you don't even have to go as far as pressing with your finger and holding to see the Download choice. You can just touch the item and it will begin to download to your books area. If you have touched it and downloaded it by mistake, you can always (while the item is still in your Carousel) touch and hold and choose remove from device. That will put it back into the Archives (Cloud) until you want it again.