We thought we knew who Americans were, but this year, spellbound by the spectacle of their presidential candidate selection process, we have seen a new side to their character that has set me wondering about its origins.

I may have found part of the answer in a list of upcoming book signings in New York. Book signings are a big deal in US cities - they combine free entertainment, the chance to interact with a celebrity and, who knows, maybe also to obtain something at RRP that may turn out to have collectable investment value one day.

But the books! The stuff these people are writing, reading and taking seriously!

Many of them sound fine. Take, for instance, The Longevity Book: The Science of Aging, the Biology of Strength and the Privilege of Time. Sounds pretty professional doesn't it? It's got "science" and "biology" in its title.

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Which well-qualified professional in matters of health and ageing penned this tome? Cameron Diaz, that's who, whose academic credentials include appearing on the cover of Seventeen when she was 17 and getting the female lead in The Mask at the age of 21.

Celebrity is the key to success in any field, it seems, whether it's best-selling authorship or a great shot at the Republican presidential nomination. Professional qualifications come second.

Although there's no denying the credibility of James A. Levine, co-director of the Mayo Clinic, no less, who will be available soon to sign your copy of Get Up!: The Dire Health Consequences of Sitting and What We Can Do About It. I know - sitting. How has this been allowed to go on for so long?

Levine is also the inventor of the treadmill desk, which is just what it sounds like.

Turns out all this sitting down in today's "chair-based world" is having "negative consequences on our health, and is a leading cause of diabetes, cancer, and heart disease".

Somewhere between Diaz and Levine - she's not a doctor, but he's never been on the cover of Seventeen - is Arianna Huffington, who will personalise your copy of her new The Sleep Revolution: Transforming Your Life One Night at a Time. Sleep, like sitting, has been around for centuries, many people do it regularly without a manual, but Huffington is here to tell you you've been doing it all wrong.

Also coming up is a chance to meet the second man to walk on the moon and have Buzz Aldrin sign your copy of No Dream Is Too High: Life Lessons from a Man Who Walked on the Moon. Apart from "being second is slightly better than being the guy who had to keep going around the moon in the spaceship" it's hard to imagine what Aldrin might have to impart that would be relevant to me.

More useful might be The Gray Rhino: How to Recognize and Act on the Obvious Dangers We Ignore, in which "Michele Wucker shows how to recognise and strategically counter looming threats". Not that she wants to make you paranoid just so you'll buy a book.

What all these books have in common is self-obsession. It's all about you. Trouble is, this exclusionary attitude has spilled over into the outside world.

A nation of people so intent on their own perfection isn't looking for a leader who will benefit anyone except themselves.

Instead a goodly - but hopefully not sufficient - number of its people are going to trust someone like Donald Trump, whose every utterance is about his amazing self - as told in such books as How to Get Rich, The Art of the Deal and Never Give Up: How I Turned My Biggest Challenges into Success.