The day that everything started to make sense

Christopher never describes himself as having Asperger's Syndrome, but it is widely accepted that this is the condition the novel explores in such detail. It is a form of autism which is often associated with high levels of intelligence, and a difficulty understanding social situations.

Can an autism diagnosis save a life? In a new documentary, reality star Christine McGuinness talks about the "huge relief" of discovering why she experiences the world differently.

Is human potential limitless? Academic prodigy Jason Arday struggled as a child, only learning to read and write in his late teenage years. For some, he highlights the best parts of the human character.

Is authenticity a modern superpower? Greta Thunberg has excoriated global leaders over their promises to address the climate emergency, dismissing them as "blah, blah, blah".

For Christopher, truth is simple: something is true or it isn't. He hates lies - he even hates novels and metaphors, because they are a form of lying. This is why he finds comfort in science and maths. But, as the adults around him know all too well, truth can also be extremely subjective.

Is democracy its biggest victim? We have long believed that the key to a free society is rational discussion in search of truth. Now some fear truth is dead - and freedom with it.

Does objective reality exist? Some physicists in the sphere of quantum mechanics argue that reality only exists in the eye of the observer. But could something so contrary to our instinct really be true?

But does it matter? Apple hopes its new $3,500 (£2,779) headset will change the way we interact with the world. Some worry its real aim is to let rich people bury their heads in the sand.

As he tells his story, Christopher often veers off into digressions about maths, logic and science - subjects he excels at. This is the reality he understands, and it is why he finds the illogical, disordered world of London so overwhelming. Does he have a point?

Is numeracy as important as literacy? Rishi Sunak has said that he wants everyone to study maths up until 18. But critics question whether this is possible - or even desirable.

Is noise the key to creativity? Silence helps people think clearly, but the latest research shows noise in the brain may be responsible for extraordinary leaps in imagination.

The Cambridge don who could not read till 18

Can premonitions be true? A new book unravels the amazing science behind a British psychiatrist who tried to predict the future by mining people's visions and dreams.

Being alone is not scary to Christopher - in fact, it is one of the only times that he can feel truly free, away from the messy and confusing influences of other people. He even fantasises about being the only person left alive on the Earth. Does isolation have to be a bad thing?

Do we need to relearn the art of hanging out? Loneliness is being described as the "modern leprosy", a debilitating personal and social problem. But what is so hard to solve about being alone?

Is alienation a modern plague? The sudden death of beloved actor Matthew Perry has shocked his fans. He faced addiction, but also the disease that defines our time: isolation.

Do we all need a soulmate? A pair of twins in their eighties assert that the secret to happiness is having a second half. Some think we should all aspire to find our twin flame.

Like all teenagers, Christopher dreams of being independent one day, although he admits that he will find this more difficult than others. But, at their heart, coming-of-age stories all share similar themes: overcoming fears, taking risks, and learning what is really important.

Is there a solution? A new survey for the BBC asked 2,000 teenagers about their biggest worries and hopes. Many fear their concerns will not be addressed.

Have we got it all wrong? A Western mother who took her baby to live in the Ecuadorian jungle found her ideas about how to be a parent turned upside down by local people.

Can we turn back time? Mental health problems are shooting up even while literacy rates plummet. Some pin the blame on the little box in your hand. But can we do without them?