Saturday night and The Genius of Gershwin. It was an audacious and imaginative decision to launch this year's Jewish Book Week with the sound of the composer of Rhapsody in Blue.

Yet, by the festival's close last Sunday, it was another colour that had registered vividly in my mind. For the event that most took me by surprise was unmistakably coloured red.

On the stage of the main hall at King's Place, King's Cross, was Anglo-Jewry's cherished rabbinical baroness, Julia Neuberger, installed as interlocutor to Andrew Solomon, psychologist and author of the book, Far From the Tree, published a couple of years ago but which I have yet to read. And an arresting sight they made, too, the baroness in flowing crimson scarf, the psychologist in impeccably scarlet trousers.

But theirs was a discussion that went many fathoms deeper than the surface signatures of fashion. Far From the Tree is a mighty book based on research into areas unknown and untrodden by most of us but which are of great significance for the understanding of human life.

Solomon - gay, Jewish and with a dyslexic childhood behind him - had spoken to, and closely observed, a wide selection of children perhaps too dismissively categorised as outsiders. Children who are dwarfs, deaf, or mentally disabled; autistic, seriously criminal or Down's Syndrome sufferers; infant prodigies or born as a result of rape.

In doing so, he encountered rich cultures, thriving communities, emphatically asserted identities and, among their families, some despair, much exhaustion and bucketfuls of love.

The concluding question at the end of this moving and instructive session was from a young woman who asked Solomon - who has a complicated family set-up at the centre of which he and his male partner have a son - how his research had influenced the parenting of his own child. "Profoundly," he answered and explained how, though by then he hardly needed to.

Another red scarf that made its mark at Jewish Book Week 2015 belonged to veteran poet Elaine Feinstein, who was reading from poems in her new collection, Portraits, alongside her interrogator Michael Schmidt at JBW's second venue, the Jewish Museum in Camden.

This time, the red scarf played a more active role as Feinstein's clip-microphone constantly became entangled in it. This somehow added a vulnerable note to the already tender nature of the verse. In between readings, Feinstein and Schmidt chatted knowledgeably about Sylvia Plath, Ted Hughes and their personal and poetic issues.

Overall, this was a strikingly informal Book Week, which is highly appropriate amid an atmosphere where friends meet and old acquaintance is repeatedly renewed, as though at some vast, intellectual wedding reception (there was even a smoked-salmon stand). The informality was apparent on both sides of the microphone. When the stages, big (the main concert hall holds 420) or small, were occupied by two speakers who knew each other well, the debate was almost invariably open and fruitful, whereas it could have been self-congratulatory and unchallenging.

Buddies Neuberger and Solomon fell into this rich category, as did journalists and friends Jonathan Freedland and Peter Beinart in a stimulating joint exposition on issues relating to coverage of, and support for, Israel from a diasporic viewpoint.

This was the theme, too, of novelist A. B. Yehoshua's passionate address as an Israeli insider to a large and receptive audience. Culture vultures all, they nonetheless soaked up Yehoshua's message that "civilisation is bigger than art" and that the "settlement of civilians" in the occupied territories is corrupting the Jewish state.

"Instead of studying the Talmud," Yehoshua urged, "read the decisions of Israel's Supreme Court."

If the joining of friends was a gamble, how much more risky was the presentation by father and son, David and Ben Crystal? David the linguist and Ben the actor came on without chair, table or notes and proceeded, with a lively and jokey session on the subject of accents, to hold their audience's attention for an hour. The same was true of Professor Steve Jones who, having made a token nod to his supposed theme of science and the Bible, gave what was in essence an undergraduate lecture on genetics and biological identity - and when the audience weren't in stitches, they were spellbound.

One of the festival's themes was "Fathers and Daughters", taking in Karl and Eleanor Marx alongside some interesting living specimens. Another focus was on the New Yorker and, with New York Times columnist Roger Cohen among others popping up in a number of places, there was a significant American presence among the 150-plus speakers. Regular British stars and stalwarts included Henry Goodman, Simon Schama, Maureen Lipman and Howard Jacobson. Subjects ranged from Ravensbrück to Middle Eastern food, Stefan Zweig to Tennessee Williams. The attendance was the highest yet at King's Place, with the venue recording over 1,800 first-time attendees.

Huge yet informal. Cerebral yet accessible. There's a bookshop. There's food.

Jewish Book Week is hard to resist. Next year in King's Cross!