The best replacement for kindle app is nook app.

The best alternatives to kindle app are rated as following:
★★★★★  nook app
★★★★★  ibooks
★★  kindle device
★★  kindle
★★  google books
★★  cloud reader
★★  kobo app
★  ibook
★  aldiko
★  ibooks app
  kindle cloud reader
  ibook app
  nook

Your alternative for kindle app is not listed? Suggest!
Speaking about kindle app, one probably shouldn't forget about text to speech.

Other search terms related to kindle app and their ratings are:
★★★★★ text to speech
★★★ amazon prime
★ buying kindle
You have in mind a companion for kindle app and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of kindle app in all years. Click on graph for more.
kindle app
nook app
ibooks