One key to YouTube monetization is having enough watch hours. Many of these video books are hours long. Watch hours can rack up faster than with shorter videos.
Free software tools are all you need. In particular Audacity and ClipChamp - both free.
Besides the public domain book option, you can create video books based on your own original content (which can be created using ChatGPT or other AI models)
In other words - you can have your own fiction without having a writing background.