A) The central theme to "A Fault In Our Stars" by John Green is to not give up on something you want to do, even if something is holding you back. The theme emerges when the main character, Hazel Grace, says that she wants to get answers to some questions she has about an unfinished book she has read, but she is being held back by lung cancer affecting her, and she wants to get those answers before it is too late. It is shown more when Hazel wants to travel from Indianapolis to Amsterdam to get the answers from the author of the book, and is determined to get there, while dealing with her cancer on the way.
B) The most complex character in the book is Hazel Grace, the main character. She is determined to get answers to questions she has about a book that was never finished, but wants to do even with her lung cancer holding her back. The other main character, Augustus Waters, comes into the story around the begging, and he meets Hazel at "Support Group" and they start being closer to each other, and eventually, he ends up helping Hazel on her journey and ends up getting her to Amsterdam.
"The Fault in Our Stars" article
