Well, 'Phoenix: Endsong' is a must-read. It delves deep into Jean Gray's connection with the Phoenix Force and her internal struggles. Another one is 'X-Men: Dark Phoenix Saga,' which is a classic that explores her transformation and the impact it has on the X-Men team.
Some of the must-read Jean Gray comics include 'Uncanny X-Men.' They showcase her powerful mutant abilities and complex character development.
I'd recommend 'All-New X-Men.' It features Jean Gray in a new light and shows her interaction with the younger versions of the X-Men. Also, 'X-Men Red' has some great Jean Gray moments that are worth checking out. These comics offer exciting storylines and character growth for Jean Gray.