I just downloaded this book for free because I was suspicious of the contents and thought it'd be another airy book filled with old quotes and obvious but encou

I just downloaded this book for free because I was suspicious of the contents and thought it'd be another airy book filled with old quotes and obvious but encouraging sentences. Now that I've read the first 3 pages I want to pay for it. Is there a way of doing this from the site itself, or do I need to "re-buy" the book?