I guess using different narrators is essential for both fiction and non-fiction books if you want the full experience. Personally, I love it when audiobooks have narrators who stick to the characters’ personalities—it just feels right. Some of the audiobooks I’ve listened to have narrators who switch up their voices for each character, and others even use a different narrator for every character, which gets really good. Narration Box has been doing a really great job with this lately