Because eBooks are largely platform-independent, several apps (some of which work with different eBook seller ecosystems) work great with the Android platform. This allows you to browse your books in the app that best suits your needs.

Amazon.com’s Kindle reader is a huge hit. One of the things that makes it so popular, besides access to a huge library of Kindle books on Amazon.com, is that Amazon offers an app for almost every device you own, and it remembers where you left off on any internet-connected device, so you can start reading on your iPhone and finish reading on your Android tablet. That doesn’t apply to some sideloaded books, but it does apply to your Amazon purchases.

Amazon's books are meant to stay in Kindle readers. It's a walled garden. They primarily use a proprietary format (azw or mobi) instead of the industry standard ePub format that all other readers use, and that forces you to stick with Amazon. You can convert unprotected book files, but that's an extra step. All of these other readers give you more freedom to move your libraries around.

Amazon offers a rental option called Kindle Unlimited, which lets you read from a large selection of the books available on Amazon (but not all of them) for $9.99 per month. The deal also includes Audible narration for some books and a selection of e-magazines, and you can read through the Kindle app — no Kindle device required. If you find yourself buying more than one book or magazine per month, this option may be the most cost-effective. Not all authors participate in Kindle Unlimited. Some find the service less than favorable for writers, as author John Scalzi explains.