Then in #52, we pick up with the storyline of Rachel Summers struggling against the Phoenix force. Professor X comes by to help. As a result of his psychic work with Rachel, we get a long history of the Force and what it has been doing through history. If you want that kind of backstory, this isn’t a bad issue to get it in.
The cover to issue #52 acknowledges that this book isn’t very good. The X-Men don’t appear in the book, except as part of the flashbacks/history of Phoenix Force.