With a graphics card from the last few years, or a Mac with Apple silicon, a book is usually made faster than it takes to listen to it. The computer stays awake while it works (the screen can still turn off).
Without a graphics card it still works, much more slowly: start it before bed and let it run. Keep a laptop plugged in, because on battery the graphics card is throttled.
VoicedByMe reads DRM-free books. Books locked to a store's own reader, like Kindle or Apple Books, can't be opened by any converter, this one included.