X-Men: The Dark Phoenix Saga

Just saw the movie.
Let's just say the comic book was not a spoiler for the movie.
While similarly themed and containing some of the same characters, the movie is not just retconned, it's wholly reimagined. It had to be to keep it to a reasonable budget.

I was inspired to re-read this by Rachel & Miles X-Plain The X-Men. It really does hold up really well as an arc, even as the Phoenix itself has come to be kind of a cliche.