Project Hail Mary is a strong option for learners who already feel comfortable with English and want a more demanding challenge. Lines are generally delivered at a comfortable pace for regular listening practice. Learners will hear plenty of useful natural English, but some lines may still require a second listen. Also, science fiction scenes can introduce technical or abstract language. Following the story requires attention, so language difficulty is not the only challenge here. It should work best near B2/C1, especially for learners prepared to handle a more complex story.