If you’ve decided that you no longer want something in your Wish List, go to the book’s info page by tapping on the book cover. You'll see a Wish List button with a filled heart beneath the Listen Now button.
If you press the heart button, it should remove the title from your Wish List section!
This is the same way that you add the book back to your Wish List section if you tap it again, by the way.
You can also remove a book by scrolling to your Wish List section, pressing the “See All” button underneath that section of your Library, and using the "Edit" function in the top right corner.
When you're done editing this section, press the "Done" button in the upper right-hand corner to save your work. You can come back and edit this section any time.
If you want to remove downloaded content, you can find out how here.
If you want to remove titles from your Listen Now section, click here.