Readwise is a free app that helps you retain your book highlights from multiple platforms in one place. With Readwise, you can synchronize your highlights from Amazon Kindle, Apple Books, Instapaper, Pocket, Medium, Goodreads, Twitter, physical books, manual input, and CSV upload. The app uses scientifically proven learning techniques called Spaced Repetition and Active Recall to resurface the right highlights at the right times using a daily email and an app, helping you retain more information.

Readwise offers additional features such as the ability to convert your best highlights into flashcards for added retention, tag, note, search, and organize your highlights within your library. The app also allows you to take highlights from your physical books and papers using your phone’s camera.

If you're not already a Readwise subscriber, you can get started immediately with a 30-day free trial with no credit card upfront. At the end of the trial, you will not be charged unless you choose to subscribe to Readwise Full or Readwise Lite.

Readwise is a must-have tool for book lovers who want to retain the key ideas from the books they read.