If you want public domain books recorded by amateurs narrators, you can hit up Librivox and Project Gutenberg and not get charged anything. The audio quality on these books is heinous. Smartphones lack anything resembling a decent microphone. Furthermore, to say that "anyone can narrate" is a lie and a disservice to people who do it professionally. To purport otherwise shows a profound lack of understanding as to what makes quality audio and professional narration performances. If you're trying to break into audio book recording, you should look into something like ACX, but only after getting some training and practice. It's a highly competitive field and few people succeed at it, let alone make a living off it.
A few small improvements
Voice recorder - Audio recorder. Best recorder for recording