I recently discovered a new e-book app that I really like. What sets this app apart is its text-to-speech (TTS) technology which can read books and documents to you. This is useful for English learners who want to improve their reading and pronunciation skills.
It has a large selection of voices and you can adjust the voice speed as well. The only thing I don't like is that the pauses between sentences are a bit too long for the best sounding "network" voices.
It has a built in store that makes it very easy to download 5000+ free classic books. Also, you can easily import books from any source or scan your device for existing books.
The free version has fairly unobtrusive ads at the bottom of the screen but you can remove them for a small fee.
Unfortunately, there isn't an iOS version.
TTS for your Web Browser
Microsoft Edge (Chromium) has a good built-in reader. It works on mobile or PC. The PC voices are the most natural sounding that I have heard.
T2S for Android : This is a mobile browser that has lots of voice options. One advantage over Edge is that it lets you listen to webpages in the background.
Pocket: This browser extension lets you save articles to read or listen to later in the mobile app. It has very natural sounding voices too. There are iOS and Android versions of the app.
imTranslator has extensions for all major browsers. It will translate and speak text that you select.