Hazel Grace Lancaster (Shailene Woodley) is 17 and has cancer.

She'd love her life to be like the cute books and films where nothing is too hard and everything ends happily, but drily adds that “it’s just not the truth”.

Her reality is one of doctor’s visits, medications and walking around with an oxygen tank because her Stage 4 cancer – while shrinking, thanks to meds – is in her lungs. A quick look at the world through Hazel’s eyes shows the sense of distance she feels from almost everyone.

There’s a wistfulness as she watches healthy teens shopping, chatting and cuddling; a layer of guilt and frustration in her relationship with her parents, particularly with her edgily cheerful mother (Laura Dern); and patient resignation – even jokes – at the doctor’s.

Matters aren’t helped by Hazel’s cancer support group, which she attends for her mother’s sake. It’s held in an Episcopalian church and the cheery cancer-surviving leader, Patrick, sings embarrassingly upbeat songs and tells the teens they are all sitting together “in the heart of Jesus”. Nothing like a good dig at glib Christians!

John Green, the author of the original book (also called The Fault In Our Stars) was actually on a path to be an Episcopalian minister until he worked as a student chaplain to kids with cancer, and found it impossible to reconcile the big “S” of suffering with the truths about God.

Writing The Fault In Our Stars was a cathartic experience, as he sought not only to deal with his own responses to the sickness and sorrow he saw during that time but bring this to life in a way that could be engaging as well as truthful. That yes, some kids have to grapple with cancer and yes, this involves a balancing act: seesawing between childhood thoughts and concerns, and maturity beyond their years. Readers around the world have responded overwhelmingly to Green’s story, and are likely to greet the film with equal enthusiasm because it is unflinchingly honest.

These teenagers are staring death and loss in the face every day, so shallowness and pretence just doesn’t cut it. They want to be real, and they demand the same of those around them because there isn’t time for anything else.

When Hazel meets the charming cancer survivor Augustus Waters (Ansel Elgort) at the support group, she isn’t impressed when he clamps a cigarette in his mouth and immediately tells him so. Then he explains that he never lights it: it’s about having control over the “killing thing”.

Augustus then floors Hazel by telling her she is beautiful. The intense friendship that follows from this unlikely first meeting is the heart of the story – not just because of the love that grows from it, as that would play into the clichés Hazel speaks of at the beginning of the film.

There is love and it is deep, strong and held with precious care.

There is also, however, the growth in Hazel and Gus and in those around them: emotional resilience, selflessness and valuing what can last when life itself is so clearly fleeting.

Thankfully the adults in the film (apart from Patrick) aren’t presented as cardboard cut-outs. We see the hurt and pain underneath the positive smiles they paste on for their children’s sake, just as we see Hazel’s desperate desire to know from her favourite author – a crusty cameo from Willem Dafoe – what happens to the characters in his book after the heroine dies of cancer.

Will they go on living? Will they manage okay? It’s her greatest worry.

The film is very faithful to the book, with dialogue regularly moved lock and stock into the characters’ mouths onscreen. Which in one sense is fine, but Augustus is so articulate and fulsome that sometimes this really doesn’t work, and it looks as though Ansel Elgort knows this. His character is much truer once Gus’s confidence is shaken and it’s less about impressive lines and more fully a performance from his heart.

Woodley, however, is brilliant as Hazel – balancing strength with vulnerability, and youthfulness with maturity, in a very poised performance. You believe every word. The Fault In Our Stars is about love, but it’s not sentimental. It’s about death, but it’s not maudlin. It’s funny, sad, joyous and sorrowful, sometimes all at once.

Because it’s about life, and life contains all these things. As Augustus says, “It’s a good life, Hazel Grace”.