I think symbolism in books are fun for the author, same as it can be in the music, and sometimes they jump at me when reading. It can also be fun to look for if you will be doing a deep dive into a single book, study an authors particular narration or things like that, but in the end the story should be engaging without the need for this at all. Good characters, good moral themes, good story world and engaging beats throughout the book.

Maynard from Tool spoke about his lyrics once, if I remember him correctly. He usually writes lyrics with a lot of metaphors, but if the music dictates another word for its sounds, he will sacrifice that word for the sound. I think that's a good attitude in both music and books - sometimes you need to sacrifice something good for a mood.