When comparing ReadEra vs FBReader, the Slant community recommends ReadEra for most people. In the question“What are the best eBook readers on Android?” ReadEra is ranked 4th while FBReader is ranked 5th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open and read book files in EPUB, PDF, DOC, RTF, TXT, DJVU, FB2, MOBI and CHM formats
Pro Very fast
Pro Completely free, no ads anywhere and anytime
Pro Supports chapters, bookmarks and page style
Pro Supports TTS
Pro Attractive interface
Looks well made and not just a txt editor or something.
Pro Kids mode
Makes it easier for kids to use the app.
Pro Built in eBook store
FBReader features an in built eBook store for users to download eBooks onto their devices through the app.

Pro Simple and fast
FBReader, while offering many options is simple in design, with that allowing for fast use.
Pro Books can be saved to SD card
Pro Cloud sync
FBReader has built in Google Drive sync for the users files, allowing them to store their eBooks online, not taking up room on their local storage.
Cons
Con No light mode
No light mode for the menu. Unusable if you have astigmatism.
Con Not many settings
Con Slow animations
Con Image sizing is wrong compared to other readers
Con Images aren't has sharp as other readers
Images don't look like they are supposed to unless you full screen the image.
Con Cannot search for books on a SD card
Con No light mode
Unusable if you have astigmatism.
Con UI is bad
User interface is confusing and ugly.
Con Complex and confusing app settings
