The Waking Up book
The Waking Up app
They share a name and an author, but otherwise should be considered separate or adjacent resources.
Further clarification:
While there is some thematic/content overlap, you absolutely should read the book, and also go through the different content in the app, as they both have merits in their own rights.
Use the app on a day-to-day basis for learning more about meditation, as well as establishing and developing your meditation practice, and read the book in your own time.
You'll get great value out of both.