Every author needs a good text-to-speech program. Here are two of my favourites.
Read Aloud is a free TTS that will read your work back to you in a flat, droning, monotone. Hearing your work read back to you in monotone can help you pick out errors that you might have missed. Plus, it’s free.
WellSaid Labs is the most lifelike TTS I’ve ever heard. Some voices are better than others, but with WellSaid labs you need to pay close attention to tell the difference. As an author, there’s nothing quite like hearing your work read back to you in a warm, professional-sounding narration.