Can anyone tell me if it's a violation of Google Play policies to forward the user to a book sale page via my app? As a developer, can I use a button to forward the user to a book page on a book sales website? Note: The book will not be consumed within the app.
Yes You can, BUT you should tag the button with an Ad
tag (like the image below)
This happened to me before in one of my apps and the Google Play Policy team asked me to clarify it is an Ad even though it linked to my own page.