I read this book earlier this year and instantly feel in love with it. I could not stop reading, but wanted to slow as the book was coming closer to the end. I'm heading to checkout the Q&A now.

yes I have read that book & loved it so much. I don't know any person whose read it and didn't love it and fall in love with Augustus.

Incomplete...no I think it ended right. Augustus died and what more is there to say?

In the comments of "Questions about The Fault in Our Stars" someone asked:
What happens to hazel grace after the book?
and another person (not John Green) replied:
I believe she and Isaac become a couple and eventually she dies from O2 depletion in her brain in her sleep and Isaac give her a eulogy and states that “though we were in love I was more in love with her when she was with Augustus, because I was in love with them both. I was in love with their love and now, though it is highly unlikely there even is an afterlife if there is I hope they are back together and waiting for me so we can play video games without having to talk to a retarded computer. Here’s to the great loves of each others life’s and mine Augustus and Hazel Grace Waters.” And he will toast them with champagne. He then lives a long happy life until he dies of an un-cancer-related death.

I really liked that comment!