Updated: October 16, 2021 
1. Lithium
Lithium adopts a material design that comes with two additional themes. My favorite night mode and sepia theme. Dark themes are easy on the eyes, especially when you are doing some night reading. Taking notes and highlighting text is easy enough. There is no 3rd party app or site integration though.
Lithium's selling point is the no bells and whistles approach with just enough features under the hood. You can play around with font settings to edit it to your liking. The pro version will remove ads and enable device sync feature using Google Drive. Simple and fast.
Pros:
- Dark theme
- Bookmarks, notes, highlight
- Font options
- Google Drive support
- No dictionary
- No 3rd party app integration
2. Amazon Kindle
You saw this coming, didn't you? Amazon offers a free app by the same name as its physical eBook reader. And you do not need a Kindle e-reader to read a Kindle e-book; you can buy the book and read it on the Kindle app on your phone. The biggest highlight of the Kindle app is sync. The app and tablet work in sync so you can leave on app, and pick up from the same place on Kindle reader. Moreover, it comes with a dictionary feature in case you can't understand the lingo. Works with both Google and Wikipedia so you can research an author, places, and whatnot. Font type, size, and background can be configured to your liking.
Amazon Kindle is free to use and connects with the eCommerce giant's large eBook store. There are millions of books that indie authors have written and published using Amazon's KDP program. All that integrates with the Kindle app. There is also a lite version. Prime members of Amazon get free access to a rotating catalog of books every month. One of the best eBook readers for Android platform.
I would like to mention Scribd here. It is Kindle's number one competitor in both eBooks and audiobooks, and comes with a subscription model. Do check it out if you use Kindle and Audible, both.
Pros:
- Bookmarks, notes, highlight
- Google, Wikipedia, dictionary
- Font options
- Show time while reading
- Realistic page turns
- Prime member benefits
- Books in multiple languages
- Kindle Store access
- No dark mode
3. Aldiko
Aldiko Book Reader supports a limited number of eBook formats like EPUB, PDF, and notable Adobe DRM-protected eBooks. The eBook reader app for Android is fluid and well designed. The virtual book shelf only adds to the beauty of the material theme. There are more options to play around with while reading books. Apart from the usual, you can also change line spacing and margin alignment.
Unlike Kindle, you can easily import your own collection which makes it favorable for folks who have collected eBooks from different sources over the years. One feature I found useful was tagging. Makes it easy to sort and search later. You can use Define and Translation feature that opens in a browser (needs Internet connection). The premium version will remove ads, allow highlighting and adding notes in EPUBs, and importing annotations for $0.99 monthly. Reasonable.
Pros:
- UI is beautiful
- Use tags
- Dictionary, translation (not offline)
- Dark mode
- Bookmarks, notes, highlight
- Import your own eBooks
- More font and reading options
- Limited eBook formats
- Subscription model
4. Prestigio
Prestigio is one of my favorite Android eBook reader app. It is highly customizable. You can work with fonts to change size, margin, and gaps. There is an online book store which will give you instant access to thousands of books in over 25 languages. One thing that even the Kindle doesn't offer is instant on-page translation. Prestigio uses Google Translation engine to do this.
Other features include bookmarks, dictionary, notes, progress bar, and background themes in white, black, and sepia. The homescreen comes with a virtual shelf which looks beautiful and gives a feeling of picking up a book from the library. Kindle is a bit limited when it comes to supporting eBook formats with all the DRM licensing. Prestigio supports almost every eBook format you could think of including EPUB, PDF, DJVU, HTML, FB2, FB2.zip, MOBI, and EPUB3.
Pros:
- Bookmarks, notes, highlight
- Google, Wikipedia, dictionary
- Font and margin options
- Realistic page turns
- Cloud storage support
- In-built store
- Books in 25 languages
- Translation
- Beautiful UI
- Dark mode, themes
- None
5. Moon+ Reader
Moon+ Reader is one of those apps that enjoy a large fan following who swear by their favorite apps. Moon+ Reader supports more eBook formats than probably any other eBook reader apps for Android. Apart from the ability to control how the fonts looks, there are options like fading edges, shadow effects, and more. There are over 20 settings for gestures, swipes, and hardware buttons like volume to turn pages. Moon+ Reader is the king of customizations. Period.
I like the dual-page mode which works amazingly well, and looks almost like a real book, especially when you are using it in landscape mode on a tablet. Other features like annotation, dictionary, translation, notes, and highlighting are all there. Supports multiple third-party apps which enables these features to work offline as well. If that wasn't enough, it supports pretty much all eBook formats as well.
Pros:
- Bookmarks, notes, highlight, annotations
- Offline dictionary and translation
- Fonts, margin, effects, alignment, fading options
- Realistic page turns
- Cloud storage support
- In-built store
- Beautiful UI
- Dark mode, themes
- Tags, authors, bookcover import,
- Number of eBook formats
- Shake to listen
- None
