Step 1: Tap 'Download Paid Version' from the Home Screen of this app, you will be re-directed to a New app called "Gutenberg Book Reader" in Apple's app store.
Step 2: Inside Apple's app store, follow instructions to complete your purchase and download this NEW app.
Step 3: Tap to open this NEW app, which is labeled as 'Gutenberg Pro' (in contrast to 'Gutenberg' for the 'free-version').
Since it is a NEW and different app, you will have to re-download any books you want to read or listen. Nothing is transferred from your current 'free-version' to this 'paid-version'.
This is a more expensive option, because you have to make two purchases, one for reading and one for listening. But you get to keep the books already downloaded and you can continue with your reading or listening without any interruptions (without having to search for the book, re-download it, and find the chapter and the page you are currently reading or listening).
Purchase 1: Unlimited Reading
Step 1: Tap 'Remove Ads interruption' from the Home Screen of this app to open the in-app purchase screen.
Step 2: Tap 'Buy' button to start Apple's standard in-app purchasing process.
Step 3: Follow instructions to complete your purchase. At the very end, you should see a message "You're all set: your purchase was successful".
Please feel free to re-purchase the same item as many times as you like to. Apple will never charge you more than once because it checks your purchase history, and if you have already purchased it, Apple will tell you so. So if for whatever reason, your purchase is not successful, please just purchase it again.
If you are not completely satisfied with your purchase, please feel most welcome to ask Apple for a refund.
Purchase 2: Unlimited listening:
Step 1: Tap 'Buy unlimited Listening' from the Home Screen of this app to open the in-app purchase screen.
Step 2: Tap 'Buy' button to start Apple's standard in-app purchasing process.
Step 3: Follow instructions to complete your purchase. At the very end, you should see a message "You're all set: your purchase was successful".