In most comic storylines, the Hulk isn't strictly immortal. He can be injured and even defeated, but his durability and regenerative abilities make him very hard to kill permanently.
I think 'Immortal Hulk: The Best Defense' is quite popular. It shows the Hulk in his new incarnation, dealing with threats not just with brute force but also with a certain kind of cunning and survival instinct that makes it a great read. Also, the art in these graphic novels is often praised, which contributes to their popularity.
The main character is, of course, the Hulk, or rather the complex entity that is both the Hulk and Bruce Banner. There are also some other characters like Betty Ross who plays an important role in the story.
One aspect that makes 'Immortal Hulk Graphic Novel' unique is its exploration of horror elements within the superhero genre. It combines the traditional Hulk smashing action with a sense of dread and the unknown. The way it portrays the Hulk as an almost unstoppable force of nature, with a touch of the supernatural, is something that sets it apart. For example, some of the scenes where the Hulk is in the shadows, and you can't quite tell what he's going to do next, create a really tense atmosphere that's not typical for a superhero comic.
Sure, She-Hulk is related to Hulk. Jennifer Walters, aka She-Hulk, got her powers because of a blood transfusion from her cousin Bruce Banner, who is Hulk. This connection is a key part of their storylines in the comics.
Captain America would be a great addition. His leadership and moral compass could guide Hulk and She - Hulk when they face difficult decisions. And his combat skills could come in handy during battles.
Comics usually depict Hulk as stronger than She-Hulk. Hulk's strength levels are often at a much higher magnitude, but it doesn't mean She-Hulk is weak by any means. She has her moments and skills that contribute to her being a significant character in the comic universe.