Sorry I haven't replied earlier, hate it when real life gets in the way of fun
Anyway. My main experience of Z games is the board games Zombies and Last Night on Earth.
Z's simplistic game play is ideal for one offs, and is adaptable to many different settings (we even did a Space hulk style variant once). LNOE has more character depth, but still plays out very much like a board game.
TWD does play more as a story, in fact it felt more like a wargame than a board game if you see what I mean. The play felt tense and in keeping with the source material. It's not blasting hordes of Zs, there are plenty of great games like that.
It does do the small group of survivors very well, and that, plus my love for the IP means I'm all in.
the expansions give you the chance to play through the story. They sound a little like the old GW LotR books; each following a section of the story and presenting it in game terms. This update https://www.kickstarter.com/projects/1744629938/the-walking-dead-all-out-war-miniatures-game/posts/1501229gives more of an idea than I could.
TLDR If you want a game that follows a group of survivors in a tense series of encounters then take a look (especially if you like the source material).
If you want a mass combat game with hordes of Zombies, it might not be what you are looking for.