I mean the story itself is a little confusing, but it was the world and the characters that I ultimately fell in love with. Also, I think it does its job well enough to set up the tone and emotion throughout the game, the ending events had me crying harder than any game within recent memory.
Ultimately what drives the game forward for me, and what kept me going was wanting to see Sam and John get through everything safely. I think the father/adoptive daughter relationship is one of the most powerful I've ever seen driven in a video game narrative, especially with a silent protagonist.