This show really helped kick off the Marvel side of comic book tv. Recently finishing up its fourth season it has been renewed for a fifth, thank goodness.
From the very beginning when we are re-introduced to Phil Coulson this show has pulled along the viewers with strong characters, interesting stories and of course a ton of action. From putting together the team, finding out about modified humans, to the fall of SHIELD, the betrayal of one of their own, to the beginnings of the Inhumans (soon to be a show of their own) to the LMDs, Ghost Rider and the whole alternate world inside a computer storylines, this show has kep abreast of the bigger movie verse yet refers to other things going on in the entirety of the Marvel universe.
While some think the show has gone downhill, I totall disagree. While having a comic book show on one of the Alphabet networks is a hard fit, this show has done well. Between schedule changes and cancellations of both the spinoff, Agent Carter and the backpedalling on other spinoffs this series holds strong and is worth watching.