Well, it can potentially have spoilers. Sometimes these comics are designed to give extra background or tease plot points that might be relevant to the game. However, it's not always a straightforward case of spoiling everything.
Yes, there could be spoilers. The comic might contain details or twists that haven't been shown in the game yet. But it also depends on how much you've already explored in the game.
It depends on your taste. If you like superhero comics with complex characters and exciting plots, then you'll likely think it's good. The world-building and character development are quite impressive.
The Invincible comic has indeed come to an end. The story reached its conclusion after a successful run. Fans have had to say goodbye to this beloved series.