Kindle is probably the best-known name in the world of eReaders. 

Kindle offers a wide selection of books, magazines and newspapers, making it one of the most popular eBook reader apps for smartphones and tablets. You don’t have to own a Kindle device to enjoy books through the Kindle app, it’s available on Android and iOS devices too. 

Kindle is powered by technology from Amazon that allows you to sync your last read page, bookmarks, highlights and notes across all devices. It also includes a built-in dictionary that makes it easy to look up new words while reading. The Kindle app provides access to Google search and Wikipedia, features that enhance your reading pleasure.

More than a million titles are available in the Kindle store, from the latest bestsellers to free classics. A customizable display lets you set font size, brightness and other settings.

A new addition is a Kindle Unlimited program that gives Kindle users access to thousands of audiobooks and e-books for a monthly fee. Overall, Kindle is the best ebooks app. 

According to tomsguide.com & lifehack.org