

Yes you need to provide both an Audio book and an ebook as inputs, if you only have one of these, you could try getting the other from your local library, or you could sail the seas. It’s not a fool proof process, so sometimes you have to try different formats of Audio books to make it work, also depending on how beefy your computer is, it will take some time to process, 1-2 hrs for big books like Stormlight Archive on my laptop
I don’t mean actively reading and listening to the audio book, think of it like English subtitles for a English movie. You can ignore them for the most part, until you hear something you didn’t quiet catch or you were not paying attention and missed something, it’s much easier to scroll back a little and read the text to catch up rather than play the part again. Happens a lot for me when listening to audio books. And rewinding the book to catch up on the part I missed is annoying, it’s better to just quickly read the last few lines instead.