It's fantastic App which extends the browser app. It's gives you almost the same functionalities with all that usefulness that provides mobile application. It gives you notifications and it's really handy in a daily routine when we don't have time siting in front on the computer. Or we just want to read our daily readwise waiting somewhere. The Readwise itself which was initially provided for the browser is a tool that you need if you collecting highlights,ecpecially on the Kindle and you never back to them. Readwise help you collecting them and remember with repetition and sending you every day some amount of them. You can customize every book: how often you would get highlights, how soon after you see one highlight it should show up again etc. Readwise also has a couple of useful features, like OCR reading, creating quizzes, search tool etc. And they are planning a couple of additional, like voice reading and improve to learning features. Really nice. I really love that app, because I currently have ~9000 highlights from books I've read and I finally start repeating, rereading them and for sure I will remember much more. BTW you can import highlights from books you haven't read from Amazon from other people. Pretty useful. It is worth every single dollar payed imo.