This is a semi-disclaimer: I devoured this book like I'd been deprived of literature. I started it Christmas morning, read it on and off all day and was finished by midnight. Because of the speed in which I read it, I'm afraid I've missed some of the essence of the book and it may be one to re-read in the future when the story is not as freshly imprinted on my mind. 
 This novel is somewhat sentimental but not to the point of being saccharine. It attempts to disconnect itself from the trite writings of fiction about terminal cancer (think "A Walk to Remember" and suchlike) and for the most part succeeds. There is, however, always going to be a level of emotionality when dealing with two lovers who, like a Shakespearean tragedy, are doomed from the start. Hazel and Gus are two intensely likeable characters, and as the reader you attempt to psychically change their fate because of Green's multi-faceted characters, and realise you cannot. That, to me, is the sign of a great novel when one unapologetically roots for the characters' well-being, particularly in a book of such morbidness. 
 The only reason why I detracted a star is because I do feel Green's writing is overly complex at times without saying much - sometimes his dialogue leans on the pretentious side (nobody speaks to each other the way Hazel and Gus do at times!) he can veer towards the trope of teen nihilists which has become over-wrought. That said, when writing about intellectual teenagers, this can be overlooked and when a book that deals with such a tragic reality as cancer and does it with humour and grace, it deserves praise. 
 (view spoiler)[The end letter will kill you off (pardon the ill-thought out pun) emotionally. You have been warned. (hide spoiler)]