Agents of SHIELD is by far the best TV show based on Comic character (beside Netflix Marvel series like Jessica Jones Luck Cage , Daredevil and Iron Fist )
the characters are well develope . It's not like typical Superhero show with particular Villian and our hero defeat him and save the world , it's very complex and well written . the story is running parallel with the Marvel's movies (but without huge spoilers ) , and make you feel that marvel's world is so big and connected .
Phil Coulson is the protagonist in the show but they don't focus on that , they give other character a very huge part in the story and you keep forgetting that there is a central character , and the character are so intersting , facinating and complex .
It's worth watching and i hope they continue produce more seasons .