There should be a matching Project Gutenberg ebook app, "gutebooks" (I have it on my Android phone) which allows you to switch back and forth between audio and

There should be a matching Project Gutenberg ebook app, "gutebooks" (I have it on my Android phone) which allows you to switch back and forth between audio and text book. Unfortunately, it doesn't seem to have an option to pay to remove adds/paid books as the audio version does.