"in a way that causes so much emotion, especially pleasure, that it cannot be described" (Cambridge University Press & Assessment 2025)

Ineffably is a good description when I read most books. I before this did not have the knowledge of the meaning of this word and now that I do I can now see how a lot of plays and poems in my past english classes have at times been ineffably fun to read watching some of the plays is ineffably theatrical and entertaing!

(https://dictionary.cambridge.org/us/dictionary/english/ineffably)