Don Quixote IS the greatest novel in English (and French and German....) It's better in Spanish, though.

In high school, I took 3 years of Spanish and two in Latin. In college I took enough Spanish literature courses for a double major with my English degree (also took up French). But I've never become fluent in speaking / writing (no immersion). In graduate school I took Classical Greek, Russian, and a course in Dante in Italian (not even close to fluent in these).

My story: I also took two quarters of Sanskrit (nobody gets fluent in this--it's an academic literary language based on various colloquial languages but was never spoken). In the first quarter were two young women from India. I think they thought that their Hindi would be a benefit, but the course was so grammatically rigorous that they didn't make it to the second quarter.

Also took a course in Proto Indo-European: 7 or so early languages in 9 weeks (Old Irish, Old High German....). Needless tp say, immersion was out of the question.